Measuring a pour
Epoxy is sold by volume, so a pour is its length times its width times its depth. A river table is measured between the edges of its slabs: the river is rarely as wide at one end as at the other, so measure it across in a few places and add each width; the calculator averages them. A tabletop to coat is its length and width, or its diameter, and the thickness of the coat. A mold is its inside length, width and depth.
A US gallon is 231 cubic inches and 128 fluid ounces (NIST), so cubic inches divided by 231 are gallons.
Worked example. A river 60 in long, 8 in wide on average and 1 1/2 in deep.
- Volume: 60 in × 8 in × 1.5 in = 720 cubic inches
- In gallons: 720 ÷ 231 = 3.12 US gallons, or 11.8 L and 399 fl oz
- With 10% extra: 3.43 gallons, 3 kits of 1.5 gal
- Layers: 1, since 1 1/2 in is less than the 2 in a layer may be
Measured at three places, 7, 10 and 10 in, the same river averages 9 in and takes 3.51 gallons.
A coat on a tabletop of 48 × 24 in at 1/8 in is 144 cubic inches: 0.62 gallons, or 80 fl oz. A round top 36 in across takes 0.55 gallons at the same thickness, and a mold of 12 × 6 in filled 2 in deep 0.62 gallons, 80 fl oz.
Layers
A deep pour gives off heat as it cures, and too much at once yellows, cracks or shrinks. TotalBoat’s sheet for its deep pour epoxy allows layers up to 2 in deep for river tables and slabs, and up to 3 in for a casting of 1 mixed gallon at most, with each layer poured once the one under it has cured and cooled. Its tabletop epoxy goes on 1/8 to 1/4 in a coat; the calculator takes 1/8 in, the thickness its coverage is worked at.
The number of layers is the depth divided by the deepest layer, rounded up: the example river at 3 in deep is 2 layers and 5 kits. Every product has its own figure: type the one on your product’s sheet under “Deepest layer”, or leave it empty for these.
Kits and the extra
A kit is the resin and the hardener together, and its size is what they make mixed. The deep pour epoxy above comes in kits of 1.5 to 6 gal, the tabletop epoxy in kits of up to 2 gal, the calculator opening on 1 gal; type the size of yours. We add 10% for what stays in the cups and on the stirrers and what soaks into the wood: set it to 0 if your figures already allow for it.
Garage floors
A floor coating is a thin film, so a kit is counted by the area it covers, not by its volume. Rust-Oleum’s sheet for its water-based garage floor kit gives about 250 sq ft a kit, at the film it recommends and with 15% of the kit counted as lost, and says one coat is enough in most cases. A floor of 20 × 20 ft is 1.6 kits, so 2; two coats take 4. Other kits cover other areas: type the figure on the label.
Common mistakes
- Measuring the river at its narrowest. Measure it in several places and let the widths be averaged.
- Pouring a deep river in one go. Past the deepest layer the product allows, the heat of the cure can crack or yellow it.
- Taking a kit’s size for the resin alone. The size that counts is what the resin and the hardener make together.
- Coating a floor by volume. A floor kit is bought by what it covers.
Questions about epoxy
How much epoxy do I need for a river table?
The river’s length times its average width times its depth, in cubic inches, divided by 231: 3.12 gallons for a river 60 in long, 8 in wide and 1 1/2 in deep, and 3.43 with 10% extra.
How deep can I pour epoxy in one layer?
As deep as your product’s sheet says. The deep pour epoxy cited here allows 2 in for a river table and 3 in for a small casting; a tabletop epoxy 1/8 to 1/4 in a coat.
How much epoxy does a tabletop take?
At 1/8 in, a top of 48 × 24 in takes 0.62 gallons, 80 fl oz.
How many fluid ounces are in a gallon of epoxy?
128, and 231 cubic inches.
How many kits do I need for a garage floor?
The floor’s area times the coats, divided by what a kit covers: 2 kits of 250 sq ft for a floor of 20 × 20 ft in one coat.
Sources
- TotalBoat, Fathom Deep Pour Epoxy, technical data (12 February 2025). Layers up to 2 in deep for river tables and slab pours, and step-pour layers where the table is to be thicker; up to 3 in deep for casting in a smaller mold, of one mixed gallon at most. Not for pours less than 1 in deep, which take longer to cure. Wait at least 36 hours before pouring the next layer. Sold in kits of 1.5, 3 and 6 gal; a gallon of mixed epoxy is 231 cubic inches. Read on .
- TotalBoat, TableTop Epoxy, technical data and instructions (8 March 2022). Do not apply it thicker than 1/8 to 1/4 in a coat; step-pour layers for a thicker coating. A mixed gallon covers 12.8 sq ft at 1/8 in. Sold as kits of two quarts, two half-gallons and two gallons, resin and hardener mixed one to one. Read on .
- Rust-Oleum, EpoxyShield Water-Based Epoxy Garage Floor Coating (Pouch Kits), technical data ESH-39 (rev. 100616). A kit of 90 fl oz of base and 30 fl oz of activator covers approximately 250 sq ft at the recommended film, assuming 15% of the material is lost. Only one coat is necessary under most circumstances. Read on .
- National Institute of Standards and Technology, Guide to the SI (Special Publication 811), Appendix B.9: conversion factors. A foot is 0.3048 m and an inch 2.54 cm, exactly. A cubic foot is 0.02831685 m³, a cubic yard 0.7645549 m³, a US gallon 3.785412 L (231 cubic inches, a cubic inch being 16.38706 mL), a US fluid ounce 29.57353 mL (128 to the gallon), a square foot 0.09290304 m² and an acre 4,046.873 m². A US dry quart is 1.101221 L. A short ton per cubic yard is 1,186.553 kg per cubic metre. Read on .
Updated . How we calculate. Found a mistake? Tell us.