Epoxy Calculator
Choose a floor coating or a resin pour (river table, tabletop, mold).
Flooring
Epoxy Calculator
Quick answer: floor coating gallons = area (ft²) × wet mils ÷ 1,604 per coat; resin pour gallons = length × width × depth in inches ÷ 231. A 440 ft² garage with two 8-mil coats needs 4.39 gallons, and a 72 × 30 × 1.5 in river that is 30% of the slab needs 4.21 gallons, before waste.
Work out epoxy for two kinds of jobs: thin-film floor coatings measured in mils, and resin pours such as river tables, tabletops, and molds measured by volume. Results come in gallons, liters, and the number of kits to buy.
How to calculate epoxy
Floor coatings and resin pours use the same unit — the U.S. gallon, which is 231 cubic inches — but they are measured differently. A floor coating is a thin film, so its thickness is given in mils (thousandths of an inch). A pour is a solid block of resin, so you work out its volume directly.
Coating: ft² × mils ÷ 1,604 | Pour: L × W × D (in) ÷ 231
= gallons per coat, or gallons of mixed resin
Where 1,604 comes from: one gallon is 231 in³. Spread 1 mil (0.001 in) thick, it covers 231 ÷ 0.001 = 231,000 in², and 231,000 ÷ 144 = 1,604 ft². So a gallon covers 1,604 ft² at 1 mil, 160 ft² at 10 mils, and 80 ft² at 20 mils.
- Floor coating: measure length × width for the area, take the wet film thickness per coat from the product data sheet, and apply the formula once per coat.
- Resin pour: measure the void in inches. For a river table, estimate what share of the slab area the river takes up and multiply by it.
- Add waste — 10% covers resin left in buckets, rollers, and squeegees, and absorption into bare concrete or wood.
- Divide by kit size and round up. Kit sizes usually state the combined volume of resin and hardener.
Worked example: two-car garage floor
A 20 × 22 ft garage (440 ft²) gets two coats at 8 wet mils.
- Per coat: 440 × 8 ÷ 1,604 = 2.19 gal (200.5 ft² per gallon)
- Two coats: 4.39 gal; with 10% extra = 4.83 gal
- In 1-gallon kits: 5 kits
Worked example: river table
A 72 × 30 in slab, 1.5 in thick, where the river is about 30% of the top.
- Full volume: 72 × 30 × 1.5 = 3,240 in³; river: 3,240 × 0.30 = 972 in³
- 972 ÷ 231 = 4.21 gal; with 10% extra = 4.63 gal (17.5 L)
Epoxy coverage by thickness
Floor coatings: theoretical coverage of one gallon per coat. Real coverage is lower on porous or rough concrete.
| Wet thickness | ft² per gallon | Gallons per 100 ft² |
|---|---|---|
| 4 mils | 401 | 0.25 |
| 6 mils | 267 | 0.37 |
| 8 mils | 201 | 0.50 |
| 10 mils | 160 | 0.62 |
| 12 mils | 134 | 0.75 |
| 16 mils | 100 | 1.00 |
| 20 mils | 80 | 1.25 |
| 125 mils (⅛ in) | 12.8 | 7.79 |
Resin pours: volume per square foot of surface at each depth.
| Pour depth | Gallons per ft² | Liters per ft² | ft² per gallon |
|---|---|---|---|
| ⅛ in | 0.078 | 0.30 | 12.8 |
| ¼ in | 0.156 | 0.59 | 6.4 |
| ½ in | 0.312 | 1.18 | 3.2 |
| ¾ in | 0.468 | 1.77 | 2.1 |
| 1 in | 0.623 | 2.36 | 1.6 |
| 2 in | 1.247 | 4.72 | 0.8 |
Wet mils, dry mils, and solids content
The 1,604 formula uses wet film thickness — what you put down. What stays on the floor depends on the product's volume solids. A 100%-solids epoxy keeps essentially all of it: 10 wet mils cures to about 10 dry mils. A water-based or solvent-based coating loses its carrier as it cures, so a 50%-solids product applied at 10 wet mils leaves about 5 dry mils. If a data sheet specifies a dry film thickness, divide it by the solids fraction to get the wet thickness to enter here.
Bare concrete also soaks up part of the first coat, especially after acid etching or grinding, which is one reason many systems use a thin primer coat. Treat the calculated figure as a minimum and let the waste allowance cover absorption.
Epoxy tips and common mistakes
- Respect the maximum pour depth. Coating and tabletop epoxies are made for thin layers; thick pours of them can overheat, yellow, or crack. Deep-pour casting resins allow thicker layers — check the per-pour limit on the label and pour in stages if needed.
- Seal the wood first. Live-edge slabs release air and absorb resin. A thin seal coat reduces bubbles and keeps the main pour from draining into the grain.
- Measure the mix ratio exactly. Most systems are 1:1 or 2:1 by volume; some specify weight. Off-ratio mixes stay soft or tacky.
- Mix only what you can place. Pot life shortens in a bucket and in warm weather. Pour floor coatings into a ribbon on the floor soon after mixing.
- Test the slab for moisture. Epoxy over a damp slab can blister or peel. A simple taped plastic-sheet test, or the method in the product instructions, comes first.
- Seal the mold. Leaks under a river-table form waste resin fast — tape and caulk every seam and add a few percent extra.
Epoxy calculator FAQ
How much epoxy do I need for a garage floor?
Multiply the floor area by the wet thickness in mils and divide by 1,604 for each coat. A 20 × 22 ft two-car garage is 440 ft²; at 8 mils one coat takes 2.19 gallons, and two coats take 4.39 gallons. Add about 10 percent for absorption and leftovers, for roughly 4.8 gallons.
How many square feet does a gallon of epoxy cover?
One gallon covers 1,604 ft² at a thickness of 1 mil, so divide 1,604 by the wet mils: about 200 ft² at 8 mils, 160 ft² at 10 mils, and 100 ft² at 16 mils. Porous or freshly ground concrete absorbs part of the first coat, so actual coverage is often lower.
How much epoxy resin do I need for a river table?
Multiply the length, width, and depth of the river in inches and divide by 231 to get gallons. A 72 × 30 in slab poured 1.5 in deep is 3,240 in³; if the river is 30 percent of the top, that is 972 in³ or 4.21 gallons. Add about 10 percent for mold leaks and wood absorption.
How do you calculate epoxy resin volume?
Volume in cubic inches is length × width × depth, all in inches. Divide by 231 for U.S. gallons or multiply by 0.0164 for liters. A 24 × 12 in tray filled 0.25 in deep holds 72 in³, which is 0.31 gallon or about 1.18 liters.
How thick should an epoxy floor coating be?
Roll-on coats are commonly applied at roughly 6 to 12 wet mils each, while self-leveling systems go down at about 1/16 to 1/8 in (roughly 63 to 125 mils). Water-based coatings shrink as they cure, so a 50 percent solids product applied at 10 wet mils leaves about 5 dry mils. Follow the product data sheet for the specified thickness.
How we built this calculator: results use the standard volume, area, and coverage formulas shown on this page, with typical U.S. material densities, bag yields, and waste factors that you can override. Written and checked by the YardsCalculator editorial team. Last reviewed: October 2026.