Epoxy Floor Calculator

How much epoxy do I need for my floor?

This epoxy floor calculator multiplies floor length × width and divides by 250 square feet per mixed gallon, giving the gallons for one coat. The formula is gallons per coat = (length × width) ÷ 250. A 24 × 20 ft two-car garage is 480 sq ft and needs 1.92 gallons per coat.

Enter the floor dimensions in feet and the price per mixed gallon. The result is not rounded, because epoxy comes in kits of different sizes. Round up to the next whole kit, and multiply by the number of coats your system calls for.

How coverage connects to film thickness

Imagine pouring a gallon of syrup on a table. Spread it wide and the layer is thin. Keep it tight and the layer is thick. Epoxy behaves the same way. One US gallon is 231 cubic inches. Spread at 100% solids over 1,604 sq ft, it leaves a film 1 mil (one-thousandth of an inch) thick.

So coverage = 1,604 ÷ mils. At 250 sq ft per gallon, the film is about 6.4 mils thick per coat. Water-based epoxies are partly water, which evaporates, so the dry film ends up thinner than the wet film.

Worked examples

1. Two-car garage: 24 ft × 20 ft, $120 per gallon

• Area: 24 × 20 = 480 sq ft
• Gallons: 480 ÷ 250 = 1.92 gallons per coat
• Cost: 1.92 × $120 = $230.40 per coat
• Two coats: 3.84 gallons. Buy two 2-gallon kits rather than three 1.5-gallon kits.

2. Three-car garage: 32 ft × 24 ft, $120 per gallon

• Area: 32 × 24 = 768 sq ft
• Gallons: 768 ÷ 250 = 3.07 gallons per coat
• Cost: $368.64 per coat
• At 3.07 gallons, a 3-gallon kit falls just short. Buy enough for 3.5 gallons or more, because porous concrete drinks up the first coat.

Epoxy coverage by film thickness (100% solids)

Wet film thickness	Coverage per gallon	Gallons for 480 sq ft
3 mils	535 sq ft	0.90
6.4 mils	250 sq ft	1.92
10 mils	160 sq ft	3.00
16 mils	100 sq ft	4.80
20 mils	80 sq ft	6.00

Primers and thin roll coats sit at the top of the table. Self-leveling and metallic systems sit toward the bottom. Use the rate printed on your product.

Solids content changes the math

Epoxy labels list a percent solids. A 100% solids product leaves all of its wet film behind as coating. A 50% solids water-based product loses half its thickness as the water evaporates. If two products are both rolled at 250 sq ft per gallon, the 100% solids coat ends up about twice as thick once dry. Compare kits by dry film thickness, not just by gallons.

How to measure your floor

• Measure wall to wall. Include alcoves, the area under shelving you will move, and the apron at the door if you plan to coat it.
• Add the stem wall or cove. If you coat a few inches up the walls, add perimeter × height in feet.
• Subtract nothing. Floor drains and posts are too small to matter.
• Check for cracks and pits. Fill them with an epoxy patch first. Deep pitting raises consumption.

Common epoxy floor mistakes

• Skipping grinding or etching. Coating a smooth, sealed slab is the most common reason epoxy peels.
• Mixing a full kit on a hot day. Heat shortens the working time. Mix only what you can spread, and work in sections.
• Ignoring hot tire pickup. Warm tires can lift poorly bonded or thin coatings. Proper prep and a full system help prevent this.
• Forgetting topcoat and flakes. Flake broadcast and a clear topcoat are separate purchases. The topcoat often covers a different area per gallon from the base.

For new concrete, wait until the slab has cured, often around 28 days. The manufacturer’s minimum cure time is on the label. To price a professional install, see the epoxy flooring cost calculator. For thin decorative overlays, compare the concrete resurfacing cost calculator. For walls, use the paint calculator.