Epoxy Resin Calculator
Enter the length, width and pour depth of your river table, bar top, casting or floor coating to get the mixed volume you need, how much resin and hardener that splits into, how many kits to buy, and what it costs.
How the math works
Epoxy is sold and mixed by volume, so the whole job reduces to one box: the length and width of the area you are covering multiplied by the depth you are filling. One US gallon is exactly 231 cubic inches, which is the only conversion the calculator needs. The waste factor covers what stays in the mixing pot, what drips off the edge, and the seal coat that soaks into the wood.
The mix ratio then splits that volume. On a 2:1 product two-thirds of every batch is resin (Part A) and one-third is hardener (Part B); on a 1:1 product it is half and half. Getting the split wrong does not slow the cure down, it breaks it — an off-ratio batch stays tacky or cures soft and it cannot be fixed by waiting.
Coverage: how far a gallon actually goes
Coverage is just volume divided by area, so depth is the number that surprises people. One US gallon is 231 cubic inches, so at a 1/8 in (3 mm) pour it covers about 12.8 ft² (1.2 m²); as a thin 1/16 in seal coat it stretches to roughly 25 ft²; at 1/4 in it drops to 6.4 ft², and at 1/2 in to only 3.2 ft². A river table 6 ft × 3 ft filled to 3/4 in therefore needs about 8.4 gallons before waste — 9.3 gallons with a 10% factor — which is far more than most first-time buyers expect. That is why deep-pour projects are usually done in two or three lifts.
Deep pour vs tabletop epoxy
They are different products and the calculator only tells you how much you need, not which to buy. Tabletop / coating epoxy cures hard in 12–24 hours, has a short pot life, and generates a lot of heat, so it is poured thin (up to about 1/4 in). Deep-pour / casting epoxy is formulated to cure slowly over 3–7 days so a thick pour can release its heat and its bubbles; it can be poured 2 in or more at a time. Pouring a tabletop product 2 in deep will exotherm, crack, smoke and possibly scorch the mould.
FAQ
- Can I measure a 2:1 ratio by weight instead of volume?
- Only if the label says the ratio is by weight. Resin and hardener have different densities, so a 2:1 volume ratio is typically closer to 100:44 by weight. Mixing a volume ratio by weight leaves the batch off-ratio and it will not cure properly.
- Why does my epoxy stay sticky?
- Almost always an incorrect ratio or inadequate mixing. Scrape the sides and bottom of the pot and mix for the full time stated on the label — usually 3 to 5 minutes — then pour into a clean second pot and mix briefly again. Uncured epoxy has to be scraped off; a fresh coat will not cure the soft one underneath.
- Should I buy extra?
- Yes. The 10% default covers normal loss. If you are doing a first-time river table, a mould with irregular edges, or a pour that has to be one continuous batch, use 15–20%. Mixed epoxy cannot be stored, but unmixed kits keep for a year or more.
- What temperature matters?
- Both room and material temperature, ideally 21–25 °C (70–77 °F). Cold resin is viscous, traps bubbles and cures slowly; hot resin has a much shorter pot life and can exotherm in the pot. Warm the unopened bottles in a water bath rather than guessing a bigger batch.
- How do I work out the cost per square foot?
- The calculator shows it. Divide the total cost by the area you are covering, and remember the depth drives it: doubling the pour depth doubles the cost per square foot.
Estimates only — always confirm the coverage rate, mix ratio and maximum pour depth printed on your specific product, and follow the manufacturer's safety data for ventilation, gloves and eye protection.