How the epoxy calculator works
Epoxy needed is the volume of the space you’re filling: area times thickness for a coating, or the inside volume of a river channel or mold. The calculator adds a waste allowance, then converts to the units on your kit and splits the total by your mix ratio [1][2].
table top: volume = length × width × thickness × coats round top: volume = π × (diameter ÷ 2)² × thickness × coats river: volume = length × (narrowest + widest) ÷ 2 × depth mold: volume = inside area × fill depth × number of molds gallons = cubic inches ÷ 231 fluid ounces = cubic inches ÷ 1.805
For example, a 96 × 48 in table coated 1 in thick holds 4,608 cubic inches, which is about 19.95 US gallons before any waste [1]. A US gallon is exactly 231 cubic inches [5].
Coverage per gallon
One gallon spread 1/8 in thick covers 231 ÷ 0.125 = 1,848 square inches, about 12.8 square feet. TotalBoat quotes about 12 square feet per mixed gallon at 1/8 in for typical table-top epoxy, which leaves a little for losses[2]. In metric, one liter spread 1 mm thick covers 1 m².
Mix ratio by volume or by weight
Resin and hardener usually weigh different amounts per cup, so a product’s ratio by weight is not the same as its ratio by volume [3]. Enter the ratio exactly as your label gives it and choose whether it’s by volume or by weight. By-volume ratios are split in fluid ounces and mL; by-weight ratios are split in grams and ounces of weight. TotalBoat’s example: 120 oz of mixed epoxy at 120A:100B by weight is 65.45 oz of resin and 54.55 oz of hardener [3].
Weight and density
To turn volume into weight the calculator uses the mixed density, 1.1 g/mL by default. That’s a rounded figure: WEST SYSTEM’s published kit weights and volumes work out to about 1.12–1.13 g/mL [4]. Your product may differ, so use its data sheet if you’re weighing.
Deep pours and layers
Epoxy gives off heat as it cures, and too thick a pour can overheat, crack or yellow. Every product has a maximum pour depth or amount on its label. Enter it, and the calculator splits a river table or casting into equal layers and tells you how much to mix for each one. Let each layer cure as the manufacturer directs before pouring the next[2].
When you’ll need more than this
- Epoxy running over the edges instead of stopping at a dam or tape.
- Porous wood that soaks up epoxy; a thin seal coat first is common.
- Uneven surfaces, knots and voids in river-table slabs.
- Your product’s minimum mix size, if your pours are very small.
This calculator estimates quantity only. Always follow your product’s technical data sheet for mix ratio, pour depth, temperature, cure time and safety.
Common questions
How much epoxy do I need for a table top?
Multiply length × width × thickness in inches and divide by 231 for gallons. A 48 × 24 in top at 1/8 in is 144 cubic inches, about 0.62 gallons (80 fl oz), or about 0.69 gallons with 10% extra.
How much does a gallon of epoxy cover?
About 12.8 square feet at 1/8 in thick, 6.4 at 1/4 in, and 25.7 at 1/16 in, before waste.
How much epoxy for a river table?
Use the river’s length, its average width and the slab thickness. A 72 in river that’s 4 in wide at its narrowest and 10 in at its widest, poured 1.5 in deep, is 72 × 7 × 1.5 = 756 cubic inches, about 3.3 gallons before waste.
How thick can I pour epoxy in one go?
It depends entirely on the product. Coating epoxies are made for thin layers, while deep-pour epoxies allow much thicker pours. Check the label and enter its maximum in the calculator to plan layers.
How many ounces are in a gallon of epoxy?
128 US fluid ounces. A “1 gallon kit” normally means the resin and hardener together make one gallon mixed.
Sources
- Omni Calculator, “Epoxy Calculator”Volume method and worked examples: 96 × 48 × 1 in table, 32 in round table at 2 in; ÷ 231 for gallons
- TotalBoat, “Epoxy Calculator”Length × width × thickness method; add 5–10% for waste; about 12 sq ft per gallon at 1/8 in; split large pours by the max pour amount
- TotalBoat Support, “How to Mix TotalBoat Epoxy by Weight”Weight ratios differ from volume ratios; worked split of 120 oz at 120A:100B
- WEST SYSTEM, “Coating Quantity”Kit weights and volumes (e.g. 2.87 lb = 1.15 L), which put mixed epoxy at about 1.1 g/mL
- NIST Special Publication 811, Appendix B.9: conversion factorsInch, pound, ounce, gallon and fluid-ounce conversions