Epoxy Resin Calculator
Surface and thickness in — total gallons out, split into resin and hardener for your exact mix ratio.
The short answer
Formula. Gallons = (area in square inches × thickness in inches) ÷ 231 — then split by the mix ratio and add your waste allowance.
Example. A 24 in × 36 in tabletop sealed at 1/8 in with 10% extra needs about 0.51 gallons total: at a 1:1 mix that is 0.26 gal resin + 0.26 gal hardener.
How this calculator works
Epoxy math is volume math in disguise. Multiply your pour's length × width × thickness, all in inches, and you get cubic inches; divide by 231 (the cubic inches in a US gallon) and you have gallons of mixed resin. A 24 × 36 in flood coat at 1/8 in thick is 24 × 36 × 0.125 = 108 cubic inches = about 0.47 gallons — call it a half-gallon kit before waste. Add your waste allowance (10% is a sane default for cup cling, bubble torch-out and the last unmixed film), then split the total by the ratio's parts.
The ratio split is where the money is, because kits are sold by total mixed volume but you measure each part. In a 2:1 by-volume system, resin is 2 ÷ (2+1) = two thirds of the total and hardener one third; in a 1:1 system, half and half; a 3:1 system is 75%/25%. One gallon mixed at 2:1 is about 85 fl oz of resin and 43 fl oz of hardener — measure both to the line, since an off-ratio pour either never cures or cures brittle. Some products quote ratios by weight (like 100:45); those are not interchangeable with volume ratios because resin and hardener have different densities, which is why the calculator carries that option separately and you should always copy the number from the specific bottle in front of you.
For river tables and deep channels, the same volume formula applies to the channel's cross-section (average width × depth × length), but thickness now matters twice: first for the gallons, second for the pour limit. Standard tabletop epoxies exotherm — heat up, yellow, crack — beyond about 1/8 to 1/4 inch per pour; deep-pour formulations tolerate 1–2 inches but cure slowly. Plan deep rivers as several calculated pours, and for irregular molds, the honest measuring stick is a water-fill test: pour water in, decant into a measuring jug, and type that number into the known-volume mode.
Sources & review date
- 231 cubic inches = 1 US gallon, exact.
- Mix ratios follow manufacturer labels (1:1 and 2:1 are the common tabletop ratios); the ratio inputs are editable.
Last reviewed: October 2026. Numbers that drift (fees, prices, densities) are editable inputs on this page.
Epoxy FAQs
How much epoxy do I need for a river table?
Treat the channel as a box: average width × depth × length in inches, divided by 231 for gallons, plus your waste allowance, poured in layers within the product's depth limit. A 2-in-deep channel 6 in wide across a 48-in table is roughly 576 cubic inches ≈ 2.5 gal mixed, poured in 2–3 sessions with standard deep-pour epoxy.
How many square feet does a gallon of epoxy cover?
At the standard 1/8-in flood coat, one gallon covers about 12.8 sq ft (231 ÷ (0.125 × 144)). Sealing coats on porous wood use less per area but need two passes; the thin seal coat math is the same formula with a thinner number.
Can I mix brands or tweak the ratio to cure faster?
No. The ratio is chemistry, not preference — off-ratio epoxy stays tacky or turns brittle, and mixing brands voids every guarantee. Buy one system, use its exact ratio, and use this calculator only for the volume arithmetic.
Why does my real pour need more than the calculator said?
Usually three things: wood absorbed a seal coat you did not count, the form or channel is wider than measured, or the pour trapped air in corners. That is exactly what the waste percentage is for — raise it to 15% for very porous or irregular pieces.