Epoxy Resin Calculator
Volume first, then the mix ratio.
Epoxy Resin Calculator
Volume (gal) = area (sq ft) x 144 x thickness (in) / 231; part A = total x A / (A + B).
Calculated instantly
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What This Calculator Does
The Epoxy Resin Calculator converts a coated area and a target film thickness into the volume of mixed resin, then splits that volume into part A and part B using your mix ratio. It is useful for countertops, garage floors, and art pieces where buying too little means a visible cold joint.
How It Works
Area in square feet is multiplied by 144 to get square inches, then by thickness in inches to get cubic inches. One US gallon is 231 cubic inches, so dividing by 231 gives gallons. Litres are gallons multiplied by 3.78541. The mix ratio divides the total into parts: a 2:1 ratio means two thirds of the volume is part A and one third is part B.
Example
A 400 sq ft floor at 20 mils is 400 x 144 x 0.020 = 1,152 cubic inches. Dividing by 231 gives 4.99 gallons, or 18.88 litres. At a 2:1 mix ratio that is 3.32 gallons of part A and 1.66 gallons of part B.
Formula
area (sq ft) x 144 x thickness (in)cubic inches / 231gallons x 3.78541total x ratio / (ratio A + ratio B)Reading the Results
Total resin volume
Mixed volume for a perfectly flat, non-absorbent surface at the stated thickness. Add primer and a margin for the substrate.
Part A
The resin side of the mix. Ratio is normally printed on the container; using the wrong side or the wrong ratio leaves a tacky or brittle cure.
Total in litres
Useful when resin is sold in litre or kilogram packs. Check whether the pack size is by volume or weight, because resin density is above 1.
Sources and References
ASTM D4414 - Measurement of Wet Film Thickness by Notch Gages
Wet film thickness measurement
A practical check that the wet coat is close to the specified thickness before it cures.
SSPC - Coating thickness and coverage guidance
Theoretical versus practical coverage
Explains why real coverage falls short of a smooth, non-porous theoretical surface.
References identify the method or data behind this calculator. Where a standard or tariff changes, the current edition applies, and the assumptions stated above take precedence over a remembered figure.
Frequently Asked Questions
Why is the resin volume so much larger than the coverage on the can?
Coverage charts usually assume a thin coat, often 1-3 mils for a sealer or 10 mils for a build coat. Volume scales linearly with thickness, so 20 mils needs twice the resin of 10 mils. Always compare the chart at your target thickness.
Does the calculator include primer and topcoat?
No. It sizes one coat. A typical system may use primer, a base coat, and a clear topcoat, each with its own thickness and coverage. Calculate each layer separately, then add the packs together.
Is the mix ratio by volume or by weight?
It depends on the product, and the difference matters because part A and part B have different densities. Use the ratio stated on the technical data sheet and measure with the method it specifies. This calculator treats the ratio as volume parts.
How much extra should I buy for a porous surface?
There is no universal allowance. Bare or broom-finished concrete can absorb a first coat heavily, and broadcast flakes add surface area. A primer and a 10-15 percent margin is a reasonable starting point, but the product data sheet and a test patch are better guides.
What happens if I mix more than I can pour in time?
Pot life shortens as temperature rises, and a batch that starts to gel will not level. Mix only what you can place within the working time, and keep part A and B separate until you are ready. Do not try to thin a gelling batch with solvent unless the product allows it.