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Epoxy Resin Calculator

Work out how much epoxy a river table, bar top, countertop, floor coat or set of coasters needs. Enter the size, pour depth and mix ratio to get the total in liters, gallons and fluid ounces, how much resin and hardener to measure, how many pours your epoxy allows and how many kits to buy.

Last updated:

Pour size
Shape

Fractions like 0.125 (1/8 in) are fine.

%

100% for coatings and molds. For a river table, the river's share of the slab area (often 20–40%).

%
Mix, pours & kits

From your epoxy's data sheet.

$
g/ml

Typically 1.05–1.20. Used for the weight estimate.

Enter your values to see the result.
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How to use the Epoxy Resin Calculator

  1. Pick the shape: rectangle for tables, countertops and floors, circle for coasters and round tops. Choose your size and depth units.
  2. Enter the length, width (or diameter) and pour depth. For a river table, set the river fill % to the share of the slab area that is open river.
  3. Add the number of pieces and a waste allowance (10% covers drips, edges, mixing cups and wood soaking up resin).
  4. Choose the mix ratio, maximum pour thickness and kit size from your epoxy's data sheet.
  5. Read the total, the resin and hardener split, the number of pours and kits, and download the pour plan if you need it.

How the epoxy volume is calculated

Epoxy is measured by volume, so the math is the same as any box or cylinder:

Volume = length × width × depth × fill % × pieces × (1 + waste %)

For a round pour, replace length × width with π × (diameter ÷ 2)². Then convert the result into the unit on your kit:

  • 1 US gallon = 231 cubic inches = 3.785 liters = 128 fluid ounces
  • 1 liter = 1,000 cm³ = 61.02 cubic inches = 33.8 fluid ounces
  • 1 fluid ounce = 1.805 cubic inches = 29.57 ml

Example: a 72 × 36 inch river table, 2 inches deep, with the river taking 30% of the area: 72 × 36 × 2 × 0.30 = 1,555.2 in³. Divided by 231 that is 6.73 gallons (25.5 L). With 10% extra you need about 7.4 gallons (28 L). At a 2:1 ratio that is about 4.9 gallons of resin and 2.5 gallons of hardener.

Epoxy needed per square foot by thickness

Mixed volume for every 1 square foot (144 in²) of surface, before waste. Multiply by your area in square feet.

ThicknessFl oz per sq ftml per sq ftSq ft per gallonTypical use
1/16 in (1.6 mm)5.014725.7Thin seal / top coat
1/8 in (3.2 mm)10.029512.8Tabletop flood coat
1/4 in (6.4 mm)20.05906.4Two flood coats, trays
1/2 in (12.7 mm)39.91,1803.2Casting, shallow molds
1 in (25.4 mm)79.82,3601.6Deep casting
2 in (50.8 mm)159.64,7200.8River tables (deep pour)

Floor coatings are usually specified in mils (thousandths of an inch): 1 gallon covers about 1,604 ÷ mils square feet, so a 10-mil coat covers roughly 160 sq ft per gallon.

Tips for accurate epoxy pours

  • Measure the real river shape. Live-edge rivers are irregular: estimate the average width of the gap and divide by the slab width to get the fill %.
  • Respect the maximum pour depth. Deep pours that exceed the rating can overheat (exotherm) and crack. Split them into layers.
  • Seal the wood first. A thin seal coat stops air bubbles and reduces how much epoxy soaks into the wood.
  • Measure the ratio exactly. Off-ratio epoxy may stay soft or tacky. Use graduated cups for ratios by volume and a scale for ratios by weight.

Frequently asked questions

How do I calculate how much epoxy I need?

Multiply length × width × depth to get the volume, then convert it: 1 US gallon is 231 cubic inches and 1 liter is 1,000 cubic centimeters. For a 72 × 36 inch river table with a 2 inch deep river covering 30% of the area, that is 72 × 36 × 2 × 0.30 = 1,555 cubic inches, about 6.7 gallons or 25.5 liters, before a waste allowance.

How much epoxy does a 1/8 inch flood coat take?

A 1/8 inch (about 3 mm) coat uses roughly 1 US gallon of mixed epoxy per 12 square feet (231 ÷ 0.125 = 1,848 square inches, or 12.8 sq ft). Seal coats are much thinner and use less, while the first coat on porous wood may need extra because the wood absorbs some resin.

What does a 2:1 mix ratio mean?

A 2:1 ratio means two parts resin (part A) to one part hardener (part B). For 3 liters of mixed epoxy you measure 2 liters of resin and 1 liter of hardener. Most ratios are given by volume; if your product lists a ratio by weight, measure by weight with a scale instead, because resin and hardener have different densities.

How thick can I pour epoxy in one layer?

It depends on the product. Tabletop and coating epoxies are usually poured about 1/8 inch (3 mm) per coat, casting resins often 1/2 to 1 inch, and deep pour epoxies 2 inches (50 mm) or more. Pouring thicker than the rated maximum can overheat, crack, yellow or bubble, so this calculator splits deep pours into several layers.

How much extra epoxy should I buy?

Plan on 10% to 15% extra for resin left in mixing cups, drips over edges, small leaks in a mold and wood absorbing resin. Live-edge slabs with bark inclusions, cracks or an open grain may need 15% to 20% more, and a thin seal coat beforehand helps stop air bubbles rising from the wood.

How heavy is cured epoxy?

Mixed epoxy typically weighs about 1.1 to 1.2 grams per milliliter, so one liter weighs roughly 1.1 kg and one US gallon about 9 to 9.5 pounds. Check your product's data sheet for the exact density.

Does the calculator store my measurements?

Only in your own browser, so the last values reappear on your next visit. Nothing is uploaded and every calculation runs on your device.

Are all the tools on FreeToolCabin tested for quality and accuracy?

Yes! Every tool on our site undergoes automated Q/A testing in real browser environments to ensure high precision, correct output, and zero errors. If you happen to spot a bug or have a suggestion, please contact us at [email protected] and our team will review it right away.

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