Articles labeled “Epoxy Math & Conversions”

The amount of pigment to add to epoxy resin depends on the pigment type, the resin quantity, and the maker's stated mixing limit. Start with the pigment maker's recommended rate, calculate the amount for your batch, and adjust only within the product instructions.

The pigment calculator can help work out an amount from your resin batch and chosen pigment rate. If the product label gives a maximum pigment percentage, use that limit rather than guessing from color strength.

How much pigment should you add to epoxy resin?

There is no single pigment percentage that suits every epoxy resin and colorant. Liquid colorants, pigment pastes, and dry powders have different compositions, so a rate that works for one product may not suit another.

Check the instructions for both the resin and the pigment. Look for the permitted pigment type, the recommended amount, and whether the rate is measured by weight or volume. If the instructions do not state a usable rate, contact the maker instead of treating an example percentage as a product recommendation.

For calculations, a pigment rate is often written as a percentage of the resin amount. A rate of 2% by weight means 2 g of pigment for every 100 g of resin. It does not mean 2% of the combined resin, hardener, and pigment weight.

That distinction matters because resin systems use different mixing ratios. Unless the pigment instructions say otherwise, calculate the pigment against the base specified by the pigment maker, not an assumed total batch weight.

How do you calculate pigment by weight?

When the instructions give a weight percentage, multiply the stated resin weight by the pigment percentage written as a decimal. A percentage is a part out of 100, so 1% becomes 0.01 and 2% becomes 0.02.

Use this formula:

Pigment weight = resin weight × pigment rate ÷ 100

For an example, assume the pigment instructions permit a rate of 2% by weight, and your example batch contains 250 g of resin. The calculation is:

250 g × 2 ÷ 100 = 5 g of pigment.

The example requires 5 g of pigment at the assumed 2% rate. This is a worked calculation, not a recommended rate for every pigment or resin.

Check the result another way. If 1% of 250 g is 2.5 g, then 2% is twice that amount, or 5 g. Both methods give the same answer.

The table shows how the calculation changes with different example batch weights. It assumes the same example rate of 2% by weight for every row.

Example pigment amounts at a 2% weight rate

Example resin weight (g)	Example pigment rate (%)	Calculation	Pigment needed (g)
100	2	100 g × 2 ÷ 100	2
250	2	250 g × 2 ÷ 100	5
500	2	500 g × 2 ÷ 100	10
750	2	750 g × 2 ÷ 100	15

Do not copy the example rate onto your product without checking its instructions. Some pigments are concentrated, while others contain carriers or fillers that change how much is needed.

Can you calculate pigment by volume?

Only use a volume calculation when the pigment instructions give a volume-based rate. If the rate is stated as milliliters per 100 mL of resin, keep both quantities in milliliters. Do not treat grams and milliliters as equal.

For an example, assume a pigment label permits 3 mL per 100 mL of resin. For an example resin volume of 400 mL, the calculation is:

400 mL × 3 mL ÷ 100 mL = 12 mL of pigment.

The units simplify to milliliters, leaving 12 mL of pigment for the example batch. You can check it by dividing 400 mL into four groups of 100 mL. Each group needs 3 mL, so 4 × 3 mL = 12 mL.

Do not convert a weight percentage into a volume amount without knowing the pigment's density. Density means the mass in a given volume. A spoonful of one pigment may weigh more than the same volume of another.

How do you use the pigment calculator?

The calculator can help with the arithmetic once you know the correct rate for your pigment. Treat its result as a calculation based on your inputs, not proof that the rate is suitable for your resin system.

1. Open the pigment calculator.
2. Enter the resin amount for your batch using the unit shown by the calculator.
3. Choose the measurement basis that matches the pigment instructions, such as weight or volume, if the calculator provides that option.
4. Enter the permitted pigment rate from the product instructions.
5. Calculate the result and check that its unit matches the way you will measure the pigment.
6. Compare the result with the product's stated maximum before adding anything to the batch.

If the calculator does not support the unit or rate shown on your product, use the formula by hand instead. Do not enter a weight rate into a volume field or assume the calculator knows the pigment's density.

What mistakes waste pigment or spoil a batch?

Errors can lead to wasted colorant or a batch that does not behave as expected. The figures below are examples showing the amount affected by a calculation mistake, not estimates of product performance.

Example pigment calculation mistakes

Mistake	Example calculation	Difference
Using 5% instead of 2%	250 g × 5 ÷ 100 = 12.5 g, compared with 5 g at 2%	7.5 g extra
Adding 2 g instead of 5 g	5 g required by the example rate, minus 2 g added	3 g short
Using the wrong batch weight	300 g × 2 ÷ 100 = 6 g, instead of 250 g × 2 ÷ 100 = 5 g	1 g extra

One common error is confusing the percentage number with a decimal. Multiplying 250 g by 2 instead of dividing by 100 gives 500 g, not the correct example amount of 5 g. That result is 100 times the amount calculated at 2%.

Another error is calculating pigment from the combined resin and hardener weight when the label defines the rate against resin alone. For example, if the resin weighs 250 g and the hardener weighs 125 g, the combined weight is 375 g. At an example rate of 2%, using the combined amount gives 7.5 g instead of 5 g, a difference of 2.5 g.

Too much pigment can also change the mixture's properties, depending on the formulation. Too little may produce a lighter color than intended. Follow the resin and pigment makers' instructions rather than trying to fix color by adding an unknown amount.

Record the batch weight, rate, and pigment amount when repeating a color. Keep the same pigment product and measurement basis; equal-looking spoonfuls do not guarantee equal pigment weights.

When is the pigment estimate unreliable?

The calculation is only as reliable as the input rate and the amount measured. It cannot predict the final shade from a percentage alone. Pigment concentration, resin clarity, layer thickness, background color, and lighting can all affect how the finished color looks.

A rate that works in a thin coating may not look the same in a deep casting. Some pigments also settle or disperse differently, so a mathematically correct amount does not guarantee an even color. Use a small trial batch only if the product instructions allow it, and keep its resin-to-hardener ratio unchanged.

Do not use the same rate across liquid dyes, pigment pastes, mica powders, and other colorants unless their instructions support that use. Check the resin maker's instructions and the pigment's safety data sheet before mixing.

For weight-based calculations, a scale must be able to measure the required amount with enough resolution. If the calculated pigment amount is smaller than the scale can reliably show, a more suitable measuring method may be needed. Do not round a tiny amount up without checking the permitted rate.

Common questions about pigment amounts

Should pigment be measured before or after mixing resin and hardener?

Follow the resin and pigment instructions, because the permitted order can vary by product. If the pigment rate is based on resin weight, calculate it from the specified resin amount rather than assuming the total mixed weight is correct.

Can you add more pigment to make the color darker?

Only add pigment within the maker's stated limit. A darker shade may require a different pigment concentration or product, and adding more than the permitted amount can affect the mixture.

Does pigment percentage mean the same thing as resin-to-hardener ratio?

No. Pigment percentage describes the colorant amount relative to a stated base quantity. The resin-to-hardener ratio specifies how much of each component to combine, and you must follow that separate instruction.

For a weight rate, 1% means 1 g of pigment per 100 g of the specified base amount. For a volume rate, 1% means 1 mL per 100 mL only when the product defines the rate that way.

To calculate different mold shape volumes, measure the inside cavity and use the formula that matches its shape. For round, box, tapered, half-sphere, and regular hexagonal molds, the result estimates how much space the resin will fill.

The mold shape calculator can help with common cavity shapes. You still need accurate measurements and the correct shape selection. The hand calculations below also let you check whether a result makes sense.

How to calculate different mold shape volumes

Start by identifying the shape of the hollow space inside your mold. Then measure the inside dimensions to the level where you want the resin to stop. Outside measurements include the mold walls and can give you the wrong volume.

Volume measures how much space a cavity holds. For resin molds, the result is often shown in milliliters (mL) or US fluid ounces (US fl oz). If you measure in centimeters, a volume of one cubic centimeter (cm³) equals one milliliter.

Use the same unit for every dimension in a formula. For example, do not enter a radius in inches and a depth in centimeters. Convert the measurements before multiplying them.

Which formula matches each mold shape?

Use the formula that matches the shape and wall profile. The following formulas assume regular shapes with straight, even surfaces unless stated otherwise.

• Box or rectangular mold: Multiply inside length by inside width and inside depth. Formula: volume = length × width × depth.
• Cylinder: Multiply pi (π) by the radius squared and then by the height. Formula: volume = π × radius² × height. The radius is half the inside diameter.
• Round tapered mold: For a mold shaped like a cone with its tip removed, use volume = π × height ÷ 3 × (R² + R × r + r²). Here, R and r are the larger and smaller inside radii.
• Half sphere: Multiply two-thirds of pi by the radius cubed. Formula: volume = ⅔ × π × radius³. This assumes a true half-sphere cavity.
• Regular hexagonal mold: Multiply the area of its hexagonal base by its depth. Formula: volume = (3√3 ÷ 2) × side length² × depth. This assumes six equal sides and straight walls.

Do not treat every tapered cavity as a round tapered mold. A square or hexagonal cavity that narrows with depth needs a formula that matches its base and taper.

How do you calculate the volume by hand?

Use the following method when you want to check a calculator result or calculate a shape without a tool.

1. Place the mold on a level surface. Decide the resin fill line before taking measurements.
2. Measure the inside dimensions. Use the diameter for a round cavity, or the inside length, width, and depth for a box.
3. Convert every dimension to the same unit. For instance, 1 inch (2.54 cm) equals 2.54 centimeters.
4. Choose the matching formula and calculate the volume. If you use centimeters, the result is in cubic centimeters, which equal milliliters.
5. For identical molds, multiply the volume of one cavity by the number of molds you will fill.
6. Decide whether to add a handling allowance. The cavity volume does not account for resin left in the mixing cup or on the stir stick.

Consider this worked example using a cylindrical mold. The example inside diameter is 6 cm (2.36 in), and the example fill height is 2.5 cm (0.98 in).

First, divide the inside diameter by two to find the radius: 6 cm ÷ 2 = 3 cm (1.18 in).

Next, apply the cylinder formula: volume = π × radius² × height.

Volume = 3.1416 × 3 cm × 3 cm × 2.5 cm = 70.69 cm³.

The estimated cavity volume is about 70.7 mL (2.39 US fl oz). This is the amount that fills the example cavity to the measured line, before any extra allowance.

The table compares several example shapes. These dimensions are examples, not standard mold sizes. The estimates assume the shape matches its stated formula.

Example volume calculations for different mold shapes

Shape	Example inside dimensions	Example calculation	Volume (mL)	Volume (US fl oz)
Cylinder	Diameter 6 cm (2.36 in); height 2.5 cm (0.98 in)	π × 3² × 2.5	70.7	2.39
Rectangular box	Length 6 cm (2.36 in); width 4 cm (1.57 in); depth 2.5 cm (0.98 in)	6 × 4 × 2.5	60.0	2.03
Half sphere	Diameter 6 cm (2.36 in)	⅔ × π × 3³	56.5	1.91
Regular hexagon	Side 3 cm (1.18 in); depth 2.5 cm (0.98 in)	(3√3 ÷ 2) × 3² × 2.5	58.5	1.98
Round tapered mold	Top diameter 4 cm (1.57 in); bottom diameter 6 cm (2.36 in); height 2.5 cm (0.98 in)	π × 2.5 ÷ 3 × (3² + 3 × 2 + 2²)	49.7	1.68

To verify a volume in milliliters as US fluid ounces, divide the milliliter amount by 29.5735. For the example cylinder, 70.7 mL ÷ 29.5735 is about 2.39 US fl oz. This conversion changes the unit, not the amount of space in the cavity.

For a batch of four identical cylindrical molds, the example total is 4 × 70.7 mL = 282.8 mL (9.56 US fl oz). If you choose an example handling allowance of 10%, the extra amount is 282.8 mL × 0.10 = 28.28 mL (0.96 US fl oz). The resulting planning quantity is about 311.1 mL (10.52 US fl oz). That percentage is an example, not a universal allowance.

How do you use the mold shape calculator?

The calculator supports cylinder, tapered, half-sphere, hexagon, and box shapes. Choose the closest match, then use the inputs to describe the inside cavity rather than its external size.

1. Open the mold shape calculator.
2. Select the mold shape that matches your cavity.
3. Measure and enter the inside dimensions requested for that shape. Keep the measurement unit consistent across all dimensions.
4. Enter how many matching molds you intend to fill, if you are calculating a batch.
5. Enter the resin density if you need the weight estimate, using the product data sheet for the appropriate value.
6. Review the volume for one mold, the total for the batch, and the amount that includes your selected allowance. Check the result units before measuring.

The calculator works from the dimensions and options entered. It cannot detect a measurement taken from the outside of a mold or know which fill line you intend to use. Compare the result with the hand formula when the cavity has a regular shape.

What mistakes lead to wasted resin?

Measurement errors can change the quantity quickly. The following table uses example calculations to show the difference that common mistakes can make.

Example measurement errors and their effects

Mistake	Example calculation	Estimated excess
Using diameter as radius	π × 6 cm × 6 cm × 2.5 cm = 282.7 mL, instead of 70.7 mL	212.0 mL (7.17 US fl oz)
Using too much depth	Using 3 cm (1.18 in) instead of 2.5 cm (0.98 in) gives 84.8 mL instead of 70.7 mL	14.1 mL (0.48 US fl oz)
Using outside dimensions	An example box measuring 6.5 cm × 4.5 cm × 3 cm (2.56 in × 1.77 in × 1.18 in) gives 87.75 mL, instead of 60.0 mL	27.75 mL (0.94 US fl oz)

Using the diameter as the radius is especially costly in the calculation. Doubling the radius makes the squared-radius term four times larger. In the example, that mistake adds 212.0 mL (7.17 US fl oz) to the estimate for one cavity.

Mixed units create another problem. If a formula uses centimeters for some dimensions and inches for others, the calculated result does not represent a valid volume. Convert first, then calculate.

Extra volume also uses more material than the cavity requires. To estimate its monetary cost, multiply the wasted volume by your actual material cost per milliliter or per US fluid ounce. Use your own purchase figures rather than assuming a fixed resin price.

Finally, cavity volume does not tell you how to combine resin and hardener. Follow the resin maker's specified mixing ratio and measurement method.

When do shape formulas become unreliable?

Formulas describe ideal shapes. A real mold may have rounded corners, sloped walls, a raised logo, deep lettering, or a curved base. These features change the space available for resin, so a formula can overestimate or underestimate the quantity.

A tapered formula also assumes a specific profile. The round tapered formula in this guide applies to a cavity whose circular cross-section changes evenly between its two ends. It is not the right formula for every mold that gets wider or narrower.

For an irregular cavity, a measured fill volume can provide a useful cross-check if the mold material permits the test liquid. Measure to the planned fill line, then dry the cavity completely before pouring resin. For handling and mixing, follow the resin maker's instructions and safety data sheet.

Rounding adds another limit. Keep extra digits during the calculation, especially when adding several small cavities. Round the final quantity to a practical measuring increment rather than rounding every intermediate result.

Common questions

Should I measure the inside or outside of a resin mold?

Measure the inside cavity because that is the space the resin must fill. Outside dimensions include the mold walls and can produce a larger estimate. Also measure to the intended fill line rather than assuming the cavity will be filled to its rim.

Does a mold volume calculation tell me the resin-to-hardener ratio?

No. The volume calculation estimates how much space the mold holds. The resin maker's instructions determine the mixing ratio and whether the components must be measured by volume or weight.

What formula should I use for a mold with rounded corners?

A box formula can give a rough estimate if the rounded parts are small, but it treats the corners as square. For a more detailed cavity, use a suitable fill-and-measure method if the mold material permits it, or use a capacity stated by the mold maker.

How do I calculate several different molds in one batch?

Calculate each cavity separately, using the formula that fits its shape. Add the individual volumes to find the total cavity volume, then decide whether a handling allowance is needed. Do not multiply one mold's volume by the batch count unless all the molds have matching dimensions and fill levels.

For volume conversion, 1 cm³ equals 1 mL, while 1 US fluid ounce is approximately 29.5735 mL. These conversions let you compare a calculated cavity volume with the markings on a measuring container.

To mix small batches of resin under 50 ml (1.69 US fluid ounces), measure the resin and hardener using the mixing ratio stated by the manufacturer. Use measuring tools suited to the small quantities involved, because a small measuring error can change the proportions more than it would in a large batch.

When mixing small batches of resin, the main challenge is measuring each component correctly. The right method depends on whether the product specifies a ratio by volume or by weight, and whether your tools can measure the required amounts.

Why are small resin batches harder to measure?

A small batch leaves less room for measuring errors. If you miss 1 ml (0.034 US fluid ounces) in a 10 ml (0.34 US fluid ounces) measurement, the error represents 10% of that amount. The same 1 ml (0.034 US fluid ounces) difference in a 100 ml (3.38 US fluid ounces) measurement represents only 1%.

This matters when a resin system requires a specific proportion of resin and hardener. Hardener is the component mixed with the resin to start the curing process. Too much or too little of either component can prevent the mixture from curing as intended.

Small batches can also be harder to mix thoroughly. Material may remain on the sides or bottom of a mixing cup, especially when the batch barely covers the bottom. A mixing method that works for a large pour may leave unmixed material in a very small batch.

There is no single minimum batch size that works for every resin product. The manufacturer's stated ratio, measurement method, and minimum recommended quantity determine whether your intended batch is suitable.

Should you measure resin by volume or by weight?

Follow the ratio and measurement method specified for your resin system. A ratio by volume compares the space occupied by each component. A ratio by weight compares their masses, usually measured with a suitable scale.

These methods are not interchangeable. Resin and hardener can have different densities, meaning equal volumes may not have equal weights. Do not convert a volume ratio into a weight ratio without reliable product-specific information.

For volume measurements, use graduated syringes or other suitable measuring containers with markings that can resolve the amounts required. Check that their graduations are appropriate for your intended batch size.

For weight measurements, use a scale with enough resolution for the smallest component. Resolution means the smallest change the scale displays. A scale that shows only whole grams may be unsuitable when the required hardener quantity is a fraction of a gram.

For example, suppose a product calls for a 2:1 ratio by volume. This example ratio means two volume parts of resin for every one volume part of hardener. It does not mean two grams of resin for every one gram of hardener.

How do you calculate a batch under 50 ml?

First, decide the total mixed volume you want to prepare. Then divide that amount according to the specified ratio. The following worked example uses a hypothetical 2:1 volume ratio and a target batch of 30 ml (1.01 US fluid ounces).

The example assumes the total target volume is the sum of the two measured components. Actual final volume can differ slightly depending on the materials and measurement conditions.

Step 1: Add the ratio parts.

Resin parts + hardener parts = 2 + 1 = 3 total parts.

Step 2: Find the volume of one part.

One part = 30 ml (1.01 US fluid ounces) ÷ 3 = 10 ml (0.34 US fluid ounces).

Step 3: Calculate the resin quantity.

Resin = 2 × 10 ml = 20 ml (0.68 US fluid ounces).

Step 4: Calculate the hardener quantity.

Hardener = 1 × 10 ml = 10 ml (0.34 US fluid ounces).

Step 5: Check the total.

20 ml + 10 ml = 30 ml (1.01 US fluid ounces).

Example component quantities for a 30 ml batch using a hypothetical 2:1 volume ratio

Component	Ratio parts	Volume (ml)	Volume (US fl oz)
Resin	2	20	0.68
Hardener	1	10	0.34
Total	3	30	1.01

To check the calculation another way, divide the resin volume by the hardener volume: 20 ÷ 10 = 2. The result matches the example's 2:1 ratio.

If you want a 45 ml (1.52 US fluid ounces) batch at the same example ratio, divide 45 ml by 3. One part is 15 ml (0.51 US fluid ounces), so the resin is 30 ml (1.01 US fluid ounces) and the hardener is 15 ml (0.51 US fluid ounces).

What is the right way to mix a small batch?

1. Read the product label and instructions. Confirm the required ratio, whether it is measured by volume or weight, and whether the product supports the intended batch size.
2. Prepare a clean, suitable mixing container and the measuring tools needed for the required quantities.
3. Measure each component separately, following the specified ratio and measurement method. Read liquid graduations at eye level where the tool design requires it.
4. Combine the components in the order stated by the manufacturer. Avoid changing the ratio to compensate for material left in a container.
5. Mix for the time and using the method specified by the product maker. Scrape the sides and bottom if the instructions call for it, so material is incorporated throughout the mixture.
6. Use the mixture within the stated working time and follow the manufacturer's curing instructions. Consult the product instructions and safety data sheet for handling and protective measures.

Do not assume that a small quantity can be mixed for less time. The correct mixing method is determined by the product instructions, not by the batch volume alone.

What mistakes waste small resin batches?

In a small batch, a little material or a small measuring error can account for a noticeable share of the total. The table below uses examples to show how errors affect quantities and costs. The prices are hypothetical, not market quotes.

Example losses and measurement errors in small-batch work

Mistake	Example calculation	Possible effect
Measuring 1 ml too much into a 10 ml component quantity	1 ml ÷ 10 ml × 100	10% quantity error
Discarding 2 ml from a 20 ml measured amount	2 ml ÷ 20 ml × 100	10% material loss
Using an example resin cost of $20 per 100 ml and wasting 5 ml	$20 ÷ 100 ml × 5 ml	$1.00 in wasted resin
Preparing twice the quantity needed	30 ml needed, 60 ml prepared	30 ml excess mixture

The cost example assumes a uniform price per milliliter. The wasted resin costs $1.00 because $20 ÷ 100 ml = $0.20 per ml, and 5 ml × $0.20 per ml = $1.00.

Another common error is using the wrong ratio basis. A correct calculation by volume will still be wrong if the product requires measurement by weight. Always check the label before calculating the components.

Rounding can also matter. If the calculation requires a quantity smaller than your measuring tool can reliably show, do not round each component independently and assume the ratio remains correct. Choose a suitable measuring method or a batch size supported by the product instructions.

When do small-batch calculations stop being reliable?

The ratio calculation tells you the intended amounts, but it cannot guarantee a successful cure. Measuring limits, material left in tools, incomplete mixing, and product-specific restrictions can affect the result.

Very small quantities may fall below the practical measuring range of a syringe or scale. If your tool cannot distinguish the required quantity from a meaningful measurement error, the calculated result may not be achievable with that tool.

Small batches may also behave differently from larger batches during curing. The amount, container shape, room conditions, and product formulation can affect working time and heat buildup. Do not assume that a product's guidance for a larger pour automatically applies to a small batch.

Finally, the ratio formula only works when the chosen total volume and ratio are appropriate for the product. It cannot replace the maker's stated minimum batch size, mixing instructions, or curing conditions. If the product does not support the quantity you intend to mix, the arithmetic alone cannot establish that the batch will cure correctly.

To convert resin ounces to ml, multiply the number of US fluid ounces by 29.5735. For example, 8 US fluid ounces equals about 236.6 milliliters (mL), but check whether your resin kit lists fluid ounces or ounces by weight before mixing.

This difference matters because fluid ounces measure volume, while ounces by weight measure mass. They are not interchangeable, and using the wrong conversion can leave a resin kit with the wrong amount of resin or hardener.

How to convert resin ounces to milliliters

Milliliters measure volume, the amount of space a liquid takes up. US fluid ounces also measure volume, so you can convert between them using a fixed conversion factor.

Use this formula:

Milliliters = US fluid ounces x 29.5735

For an example amount of 4 US fl oz, the calculation is:

4 x 29.5735 = 118.294 mL, which rounds to 118.3 mL.

The reverse conversion works by dividing milliliters by 29.5735. For example, 250 mL ÷ 29.5735 = about 8.45 US fl oz.

These conversions use US fluid ounces. Imperial fluid ounces, used in the UK measurement system, have a different size. If your kit uses imperial units, confirm the unit before applying this chart.

Resin ounces to ml conversion chart

Use this chart to convert common example quantities from US fluid ounces to milliliters. The values are rounded to one decimal place, so small differences may appear if you calculate with fewer decimal places.

US fluid ounces converted to milliliters

US fluid ounces (fl oz)	Milliliters (mL)	Approximate liters (L)
1 fl oz	29.6 mL	0.030 L
2 fl oz	59.1 mL	0.059 L
4 fl oz	118.3 mL	0.118 L
6 fl oz	177.4 mL	0.177 L
8 fl oz	236.6 mL	0.237 L
10 fl oz	295.7 mL	0.296 L
12 fl oz	354.9 mL	0.355 L
16 fl oz	473.2 mL	0.473 L
24 fl oz	709.8 mL	0.710 L
32 fl oz	946.4 mL	0.946 L

To convert milliliters to liters, divide by 1,000. For example, 500 mL equals 0.5 L. This is useful when a kit lists its total volume in liters but your measuring cup uses milliliters.

How to read a resin kit's mixing ratio

A mixing ratio tells you how much resin to combine with how much hardener. The ratio may be given by volume or by weight, and the distinction affects how you measure each part.

An example kit labeled with a 2:1 ratio by volume calls for two equal volume units of resin for every one volume unit of hardener. If the example resin amount is 100 mL, the matching hardener amount is 50 mL, making 150 mL total before mixing effects.

A ratio by weight works differently. It compares the mass of each component, so measuring the same ratio with a volume cup may give the wrong result. Use the measurement method specified by the kit maker.

Converting ounces to milliliters does not tell you the correct mixing ratio. It only converts a volume measurement. Check the kit label or instructions to find the required ratio and whether it is measured by volume or weight.

How to use a mix ratio calculator

A mix ratio calculator can help work out the amounts of resin and hardener after you know the kit's stated ratio. It does not replace the kit instructions, and its result is only useful when you enter the correct ratio and measurement method.

1. Find the mixing ratio printed on the kit instructions.
2. Confirm whether the ratio is by volume or by weight.
3. Enter the ratio as written by the maker.
4. Enter the amount of resin you plan to measure, using the unit the calculator accepts.
5. Read the calculated hardener amount and check its unit before measuring.

If you have only an amount in US fluid ounces, convert that volume to milliliters first when needed. Do not use a volume conversion to replace a weight-based measurement.

Worked example: converting a resin kit amount

Suppose an example project calls for 12 US fl oz of mixed liquid by volume. To convert that amount to milliliters, multiply 12 by 29.5735.

12 x 29.5735 = 354.882 mL.

Rounded to one decimal place, the example total is 354.9 mL, or about 0.355 L. This is the converted volume, not a recommendation for a particular project or kit.

Now suppose an example kit uses a 2:1 ratio by volume and you want to prepare that total amount. The ratio has three parts altogether: two parts resin and one part hardener.

Divide the total volume by three: 354.9 mL ÷ 3 = 118.3 mL per part, using the rounded total.

Calculate the resin amount: 2 x 118.3 mL = 236.6 mL.

The hardener amount is one part, or 118.3 mL. Together, the rounded amounts give 236.6 mL + 118.3 mL = 354.9 mL.

Keep in mind that this example applies only to a ratio stated by volume. If a kit gives its ratio by weight, calculate the component masses instead and use the maker's specified measurement method.

Common conversion mistakes and their costs

The first mistake is treating ounces by weight as fluid ounces. For example, 8 oz by weight means a mass of about 226.8 g, while 8 US fl oz means a volume of about 236.6 mL. These figures describe different properties, so you cannot swap one for the other without additional information about the liquid.

The second mistake is using the wrong fluid-ounce system. Eight US fl oz converts to about 236.6 mL. Eight Imperial fl oz converts to about 227.3 mL. The difference is about 9.3 mL, which can affect a measured batch.

A third mistake is rounding too early. If you convert each small component separately and round each result, the final total may differ slightly from a calculation using full precision. Keep extra decimal places during the calculation and round the final measurement to a level your measuring tool can support.

Another mistake is using the correct conversion with the wrong mixing ratio. A perfect conversion cannot fix an incorrect resin-to-hardener proportion. Follow the maker's instructions and safety data sheet for mixing and handling.

When the conversion method is not enough

The fluid-ounce conversion is reliable when the starting unit is a US fluid ounce and the target is milliliters. It cannot identify whether a label means fluid ounces or ounces by weight, so the unit description matters.

It also cannot tell you whether a resin kit's ratio is by volume or weight, how much material a surface needs, or whether a product is suitable for a planned pour. Those details come from the kit instructions and the measurements for your project.

For a weight-based ratio, you need the component masses or the correct weighing instructions. Do not infer a resin's mass from its volume unless you have a reliable density value for that specific material.

Frequently asked questions

How many milliliters are in 1 US fluid ounce of resin?

One US fluid ounce equals about 29.6 mL. This is a volume conversion and applies regardless of the liquid's brand, although the same volume can have a different mass for different liquids.

Is 1 ounce of resin the same as 30 mL?

It is a useful rounded estimate if the ounce means a US fluid ounce. The more precise conversion is about 29.5735 mL, so 30 mL is slightly higher.

Can I measure resin and hardener in milliliters?

Yes, when the kit specifies a mixing ratio by volume. If the ratio is by weight, use the maker's required weighing method instead of measuring both components by volume.

A resin data sheet tells you how a particular resin is meant to be measured, mixed, and used. The density, mixing ratio, and maximum pour depth help you calculate material quantities and avoid mistakes that can affect the finished piece.

If you are estimating material for a project, an epoxy resin calculator can help you work out the required volume. Read the product's data sheet first, because a calculator cannot determine the correct specifications for an unidentified resin.

What does a resin data sheet tell you?

A technical data sheet, often called a TDS, describes a product's properties and recommended working conditions. For a two-part epoxy system, it may list the mixing ratio, density, working time, curing time, and permitted casting depth.

The sheet may also distinguish between resin and hardener specifications. These are separate components, so do not assume that a value listed for one applies to the other or to the combined mixture.

Three details are especially useful when planning a project. Density helps convert volume into mass, the mixing ratio tells you how much of each component to combine, and the pour-depth limit describes how deeply the product can be poured under its stated conditions.

How do you read density on a resin data sheet?

Density describes how much mass fits into a given volume. It is commonly written in grams per milliliter (g/mL) or kilograms per liter (kg/L).

For example, a density of 1.1 g/mL means that 1 mL of the stated material has a mass of 1.1 g under the stated measurement conditions. The equivalent density is 1.1 kg/L.

Density is useful when a project plan gives a volume but you need an estimated mass. Multiply the volume by the matching density, using compatible units.

Example density calculation using illustrative values

Step	Example calculation
Required volume	500 mL (16.9 US fl oz)
Example density	1.1 g/mL
Mass calculation	500 mL × 1.1 g/mL = 550 g
Approximate US mass	550 g = 19.4 oz

Check the arithmetic another way: 1.1 g/mL is 1,100 g/L, and 0.5 L × 1,100 g/L equals 550 g. Both calculations give the same result.

This example assumes that the stated density applies to the material being measured. If the sheet lists separate densities for resin and hardener, use the relevant value for each component rather than treating them as identical.

What does the mixing ratio mean?

The mixing ratio states how much resin and hardener must be combined. It may be given by volume or by weight, and those methods are not automatically interchangeable.

For example, a product with a 2:1 ratio by volume requires two volume parts of resin for every one volume part of hardener. If the instructions instead specify a weight ratio, the amounts must be measured by mass.

For a worked example, suppose the data sheet specifies a 2:1 volume ratio and you want 300 mL (10.1 US fl oz) of mixed material. Add the ratio parts, divide the target volume by that total, and multiply by each component's share.

Example calculation for a 2:1 volume ratio

Step	Example calculation
Total ratio parts	2 + 1 = 3
Volume per part	300 mL ÷ 3 = 100 mL
Resin amount	2 × 100 mL = 200 mL
Hardener amount	1 × 100 mL = 100 mL
Total check	200 mL + 100 mL = 300 mL

Check the ratio by dividing 200 mL by 100 mL. The result is 2, confirming the required 2:1 proportion. These are example quantities, not a recommendation for an unspecified product.

One detail matters when working from a weight ratio: the total mass of the mixture is not the same as its volume. Do not use a volume calculator to convert between them unless the required density information and measurement method are known.

What does maximum pour depth mean?

Pour depth is the height of resin in the mold, measured vertically from the bottom of the resin layer to its surface. It is different from the total volume needed to fill a mold.

The maximum pour depth is a product-specific limit under stated conditions. A deeper layer may retain more heat during curing, and the allowed depth can change with the formulation, mold, batch size, and working conditions.

Do not assume that every epoxy can be poured to the same depth. A coating resin and a casting resin may have different intended uses, even if both are sold as epoxy.

For a rectangular mold, you can estimate the required volume from its internal dimensions. Multiply the inside length by the inside width and by the intended resin depth. Keep all three measurements in the same units.

Example rectangular mold volume calculation

Measurement	Example value
Inside length	30 cm (11.81 in)
Inside width	20 cm (7.87 in)
Intended depth	2 cm (0.79 in)
Volume calculation	30 × 20 × 2 = 1,200 cm³
Equivalent volume	1,200 mL (40.6 US fl oz)

The reverse check is 1,200 cm³ ÷ (30 cm × 20 cm) = 2 cm of depth. The arithmetic is consistent, but the calculated volume does not prove that the product can be poured at that depth.

Check the manufacturer's stated maximum depth before using the result. If the product requires several layers, calculate each layer separately and follow its recoat instructions.

How to use an epoxy resin calculator with a data sheet

A calculator can help with the arithmetic once you have identified the product's specifications. Use the data sheet to supply the correct values rather than guessing the ratio or permitted depth.

1. Find the mixing ratio on the data sheet and note whether it is by volume or weight.
2. Measure the mold's internal length, width, and intended fill depth, using consistent units.
3. Enter the dimensions or target volume into the calculator, matching its measurement units.
4. Enter the correct mixing ratio if the calculator provides ratio inputs.
5. Review the calculated amount and compare the planned pour depth with the product's stated limit.
6. Check whether the calculator estimates volume, mass, or both before using its result to measure material.

If the calculator does not support the ratio method listed on the data sheet, calculate the mixture by hand. A correct calculation still depends on accurate measurements and the right product specifications.

Which mistakes cause the biggest calculation errors?

• Confusing volume with mass: A 500 mL volume is not automatically 500 g. At the illustrative density of 1.1 g/mL, it corresponds to 550 g, a difference of 50 g.
• Using the wrong ratio method: A volume ratio cannot be treated as a weight ratio without suitable product data. The resulting component amounts may be wrong even when the ratio arithmetic looks correct.
• Measuring external mold dimensions: A mold's outer dimensions may overstate its internal capacity. The error depends on wall thickness and shape, so measure the cavity that will hold the resin.
• Ignoring the depth limit: A mold may have enough capacity for a deep pour, but the resin may not be designed for that depth. Extra material can be wasted if the project must be divided into layers.
• Rounding too early: Rounding each component before finishing the calculation can introduce avoidable measurement errors. Keep the working figures until the final amount, then round to match the measuring equipment.

When handling or disposing of resin components, follow the manufacturer's instructions and safety data sheet for the specific product.

When are these calculations less reliable?

Density calculations depend on the stated material and measurement conditions. Temperature can affect density, and a value for one component may not describe the combined mixture exactly.

Mold-volume calculations also assume a regular shape with known internal dimensions. Curved molds, sloped walls, embedded objects, and uneven surfaces can change the amount required.

Finally, a calculated volume cannot predict every curing result. The arithmetic does not establish the correct pour depth, working time, curing time, or suitability of a product for a particular project.

When the data sheet gives a range or a condition for a stated value, use that information rather than treating the number as universal. The product's own instructions determine which density, ratio, and depth limits apply.

Use the basis that the resin's data sheet gives for the mix ratio. If the sheet gives the ratio by weight, weigh both parts. If it gives the ratio by volume, measure both parts by volume.

The data sheet is the maker's technical sheet for the product. Part A is the resin and part B is the hardener. A resin mix by weight or volume is not a free choice. The two ratios are different numbers whenever part A and part B differ in density. The resin mix ratio calculator converts one into the other.

Why the two ratios are different numbers

Volume is the space a liquid fills, in milliliters (ml) or US fluid ounces (fl oz). Weight here means mass, in grams (g) or ounces (oz). Density links them. Density is the mass of one milliliter, in g/ml, and the data sheet lists it for each part.

In words: mass equals volume times density. With symbols: mass (g) = volume (ml) × density (g/ml).

If part A is denser than part B, one milliliter of A weighs more than one milliliter of B. A ratio by volume then needs a different set of numbers when you move to the scale. To go from volume to weight, multiply each volume part by that part's density. To go from weight to volume, divide each weight part by its density.

If both parts had the same density, the two ratios would match and the choice would not matter. You cannot know that from the numbers alone, so check the data sheet.

Worked example: converting a ratio both ways

The densities here are examples, not values for any real product. Part A is 1.10 g/ml and part B is 1.00 g/ml. The ratios 2 to 1 and 100 to 45 are also examples.

Converting a ratio between volume and weight, using example densities

Starting ratio	Part A	Part B	Result
2 to 1 by volume, to weight	2 × 1.10 = 2.20	1 × 1.00 = 1.00	2.20 to 1 by weight
100 to 45 by weight, to volume	100 ÷ 1.10 = 90.91	45 ÷ 1.00 = 45.00	90.91 ÷ 45 = 2.02 to 1 by volume

Now a full batch. Take a ratio of 100 to 45 by weight and a total of 500 g. Part A is 500 × 100 ÷ 145 = 344.83 g. Part B is 500 × 45 ÷ 145 = 155.17 g. Dividing each by its density gives the volume of each part.

One 500 g batch at 100 to 45 by weight, in metric and US units

Part	Grams	Ounces	Milliliters	US fl oz
A	344.83	12.16	344.83 ÷ 1.10 = 313.48	10.60
B	155.17	5.47	155.17 ÷ 1.00 = 155.17	5.25
Total	500.00	17.64	468.65	15.85

One ounce is 28.3495 g and one US fluid ounce is 29.5735 ml. The mix ratio calculator gives these figures when you enter the ratio and both densities. For a larger pour, find the total first.

How to measure each way

By weight, on a scale

1. Put the empty cup on the scale and tare it. To tare is to set the display to zero with the cup on it.
2. Pour part A until the display shows its target mass.
3. Tare again, then pour part B until the display shows its target mass.
4. Stir for the time on the data sheet and scrape the sides and bottom of the cup.

A scale shows steps, such as 1 g. If the display moves in 1 g steps, the true mass can be up to 0.5 g off. On a 5 g target (an example), 0.5 g is 10%. Small batches need a finer scale, and the article on mixing small batches under 50 ml covers them.

By volume, in a marked cup

1. Set the cup on a flat surface and read the line at eye level.
2. Fill to the line for part A, then measure part B the same way.
3. Stir for the time on the data sheet and scrape the sides and bottom of the cup.

You can check a cup's lines with water. One milliliter of water weighs about 1 g. Fill to the 100 ml line, weigh the water, and compare the reading with 100 g.

Mistakes and the size of each error

One slip is to read a weight ratio and measure it as volume, or the reverse. The error equals the ratio of the two densities. These rows use the example densities from above.

Using the wrong basis, with example densities

Data sheet says	You do	What you actually mix	Size of the error
100 to 45 by weight	Measure 100 ml and 45 ml	110 g and 45 g, which is 2.44 to 1 instead of 2.22 to 1	Part A is 10% too heavy (1.10 ÷ 1.00)
2 to 1 by volume	Weigh 2 g and 1 g	1.82 ml and 1.00 ml, which is 1.82 to 1 instead of 2 to 1	Part A is 9.1% too small (1.82 ÷ 2)

The article on why resin cures sticky looks at ratio errors like these in more detail.

Special cases

A volume ratio can be weighed once you convert it. Take a total of 300 ml at 2 to 1 by volume, with the example densities. Part A is 300 × 2 ÷ 3 = 200 ml, which weighs 200 × 1.10 = 220 g. Part B is 300 × 1 ÷ 3 = 100 ml, which weighs 100 × 1.00 = 100 g. The batch weighs 320 g, or 11.29 oz.

Changing the batch size keeps the ratio, not the amounts. Multiply both parts by the same factor, on the same basis. A batch twice as big needs twice the grams of A and twice the grams of B.

If you pour too much of part A on a scale, you cannot take it back, but you can raise part B to match. Take a target of 100 g of A and 45 g of B (an example). You pour 108 g of A. Part B must then be 108 × 45 ÷ 100 = 48.6 g, and the batch is 108 + 48.6 = 156.6 g. Check that your cup holds the larger total before you add part B.

Which basis to choose

Choosing a basis from what the data sheet gives

The data sheet gives	What to do
A ratio by weight	Weigh both parts on a scale.
A ratio by volume	Measure both parts by volume, or convert the ratio to weight with both densities.
Both ratios	Use either one, and use the same one for the whole batch.
A ratio but no density	Stay on the basis the sheet states, or find the densities as described below.

Where the answer stops being reliable

A conversion is only as good as the densities you enter. Density changes slightly with temperature, so the figure applies at the temperature the data sheet states. The sheet may also round the ratio, for example to 2 to 1, and the calculator cannot see the unrounded value. The article on reading a resin data sheet shows where to find density, ratio and pour depth.

The sums also cannot tell you how much error the resin tolerates. That limit comes from the maker, and this article does not state it.

If the data sheet gives no density, you can find it yourself. Measure a known volume of one part, weigh it, and divide the mass by the volume. In an example where 100 ml of part A weighs 110 g, the density is 110 ÷ 100 = 1.10 g/ml. The reading is only as exact as the cup's lines, so check them with water first, and repeat for part B.