Epoxy Floor Calculator

Calculate how many gallons of epoxy floor coating you need for a garage or basement from the floor size, number of coats and coverage per gallon, plus kits and flakes.

By CalcBuilt Editorial TeamUpdated September 9, 2026Formulas checked against manufacturer specs, see how we calculate.

Quick answer: To find how much epoxy you need, multiply the floor area by the number of coats, divide by the coverage per gallon printed on the kit, then add 10% for waste. A 20 x 20 ft garage (400 sq ft) with two coats at 250 sq ft per gallon needs 3.2 gallons, or 3.52 gallons with waste, which is 2 kits of 3 gallons.

Your measurements

Plan view from above: area is length times width.

Floor lengthftFloor widthftCoatsA colored base coat plus a clear top coat is the usual two-coat system. Count a primer as a coat if the kit includes one; a full flake broadcast needs two clear coats, so enter 3.Coverage per gallonsq ft/galPrinted on the kit. 100% solids epoxy at 10 mils covers about 160 sq ft per gallon, water-based about 300. A ground or porous slab drinks 20 to 30% more on the first coat.Kit size (gallons)Mixed volume of one kit, resin plus hardener. 100% solids kits are usually 3 gal (2 gal resin, 1 gal hardener); box-store water-based two-car kits are 2 gal. Never split a kit by eye.Decorative flakesWaste allowance%10% covers material left in the bucket and roller, and a rough or porous slab that soaks up the first coat. A kit that kicks in the bucket is a total loss, so waste is not a substitute for working fast.

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Epoxy needed3.52 galAll results

Results

Epoxy needed: 3.52 gal; 3.2 gal for 2 coats at 250 sq ft per gallon, plus 10% waste
Kits to buy: 2 kits of 3 gal; 6 gal purchased. Kits are labeled by mixed volume, so check the can. Mix a whole kit at a time; an off-ratio half kit stays tacky
Decorative flakes: 0 lb; No flakes selected
Floor area: 400 sq ft; 800 sq ft of total coverage across 2 coats

Epoxy Floor formula

Floor area (sq ft) = Length (ft) x Width (ft)
Gallons = Floor area x Coats / Coverage per gallon x (1 + waste %)
Kits = Gallons / Kit size, rounded up
Flakes (lb) = Floor area / 100 x broadcast rate  (light 0.5 lb, full 10 lb per 100 sq ft)

Worked example

A 24 x 24 ft two-car garage coated with a 100% solids kit rated at 200 sq ft per gallon, two coats: 24 x 24 = 576 sq ft. 576 x 2 / 200 = 5.76 gallons. Add 10% waste: 5.76 x 1.1 = 6.34 gallons. With 3 gallon kits, 6.34 / 3 = 2.11, so buy 3 kits.

For a full flake broadcast on the same floor: 576 / 100 x 10 = 57.6 lb of flakes, so buy 60 lb. A light sprinkle would need only 576 / 100 x 0.5 = 2.9 lb.

Quick reference

Epoxy needed for common floors, two coats at 250 sq ft per gallon with 10% waste
Floor	Area	Gallons	3 gal kits
12 x 22 ft one-car garage	264 sq ft	2.32	1
20 x 20 ft two-car garage	400 sq ft	3.52	2
22 x 22 ft garage	484 sq ft	4.26	2
24 x 24 ft garage	576 sq ft	5.07	2
30 x 22 ft three-car garage	660 sq ft	5.81	2
30 x 40 ft basement	1,200 sq ft	10.56	4

How to calculate epoxy for a floor

Measure the floor length and width and multiply for the area; the whole slab gets coated, so there is nothing to subtract. Multiply the area by the number of coats, then divide by the coverage rate on the kit. Coverage is the number that matters most. 100% solids at 10 mils spreads about 160 sq ft per gallon, so a 3 gallon kit is one coat on a two-car garage. A water-based kit at 300 sq ft per gallon lays down about 5 mils wet and half that dry, which is why it wears through under tires.

Add 10% for waste. A ground slab drinks 20 to 30% more on the first coat, and a few ounces stay in the bucket and roller. Pot life for 100% solids is about 30 to 40 minutes at 70 F, and much less if the mixed kit sits in the bucket heating itself. Pour it out in a ribbon within 5 minutes, spread with a notched squeegee and back-roll. Never split a kit by eye; the ratio is by volume and an off-ratio batch stays tacky for good.

Prep, kits and flakes

Prep decides whether the coating lasts. Acid etching gives a CSP 1 profile (ICRI 310.2R), enough for a thin water-based kit only, and leaves salts unless neutralized and rinsed twice. For 100% solids, grind with a diamond cup wheel to CSP 2 to 3 and vacuum; a slab under 28 days old is not ready. Tape a 2 x 2 ft square of plastic to the floor for 16 hours (ASTM D4263); condensation under it fails the slab. A calcium chloride test (ASTM F1869) over 3 lb per 1,000 sq ft per 24 hours, or 75% on an RH probe (ASTM F2170), calls for a moisture-mitigating primer.

Coat at 55 F (13 C) or above with the slab at least 5 F over the dew point. Put the top coat on inside the recoat window on the label, usually 12 to 24 hours. Past 48 to 72 hours, sand with 120 grit and wipe, or the top coat peels. Broadcast flakes into the wet base coat, scrape the loose ones the next day, then clear; a full broadcast uses about 10 lb per 100 sq ft, a light sprinkle half a pound. A garage that gets parked in wants a polyaspartic top coat, which resists hot tire pickup and UV yellowing better than clear epoxy.

What this calculator leaves out

Grinder rental (typically $75 to $150 a day plus a diamond cup wheel), degreaser, crack filler for joints and spalls, and a moisture primer if the slab fails the test. Anti-slip aggregate is a separate 1 lb jar stirred into the top coat. Add a notched squeegee, 3/8 in lint-free roller covers, spiked shoes and a respirator with organic vapor cartridges.

Mistakes that cost money

Acid etch under 100% solids epoxy leaves a CSP 1 profile and the coat peels in sheets; grind to CSP 2 to 3 (ICRI 310.2R).
Skipping the moisture test: vapor over 3 lb per 1,000 sq ft (ASTM F1869) blisters epoxy; use a moisture-mitigating primer or a breathable coating.
Mixed 100% solids kicks in the bucket in 20 to 30 minutes; pour it out in a ribbon at once and squeegee it.
Missing the recoat window (usually 12 to 24 hours) means the top coat peels; past 48 hours sand with 120 grit and wipe first.
A thin water-based kit at 3 to 4 mils lifts under hot tires; a parked-in garage needs 100% solids and a polyaspartic top coat.
Coating below 55 F or a slab within 5 F of dew point leaves a soft, blushed film; measure the slab, not the air.

Key facts

One gallon of any coating covers 1,604 sq ft at 1 mil thick, so coverage per gallon equals 1,604 divided by the wet film thickness in mils.
100% solids epoxy applied at 10 mils covers about 160 sq ft per gallon; thin water-based garage kits spread to 250 to 300 sq ft per gallon.
A standard two-car garage is about 20 x 20 ft, or 400 sq ft; a 24 x 24 ft garage is 576 sq ft.
Vinyl flakes are broadcast at roughly 0.5 lb per 100 sq ft for a light accent and 8 to 10 lb per 100 sq ft for full coverage.
Most epoxy floors accept foot traffic after 12 to 24 hours and vehicles after 3 to 7 days of cure, depending on temperature.

Frequently asked questions

How much epoxy do I need for a 2-car garage?

A 20 x 20 ft garage is 400 sq ft. At 250 sq ft per gallon, two coats take 3.2 gallons, or about 3.5 gallons with 10% waste, so plan on two 3 gallon kits, one per coat.

How many square feet does a gallon of epoxy cover?

It depends on the film thickness: 1,604 sq ft at 1 mil. That is 160 sq ft at 10 mils for 100% solids and roughly 250 to 300 sq ft for a thin water-based kit. Use the coverage printed on your kit, and expect a ground slab to drink more on the first coat.

Do I have to grind the concrete, or is acid etching enough?

Etching gives a CSP 1 profile, which only holds a thin water-based kit and fails if the salts are not rinsed off. For 100% solids, rent a grinder with a diamond cup wheel and take the slab to CSP 2 to 3 (ICRI 310.2R). Most peeling and hot tire pickup traces back to an etched-only floor.

How many pounds of flakes do I need?

About 0.5 lb per 100 sq ft for a light accent and 10 lb per 100 sq ft for full coverage where no base color shows through. A 400 sq ft garage takes 2 lb light or 40 lb full.

Sources and references

EpoxyShield Garage Floor Coating kit product page (Rust-Oleum)
Calculating coating requirements: 1,604 sq ft per gallon at 1 mil (Dampney)
What's a mil? Coverage per gallon by film thickness (Seal-Krete (Rust-Oleum))
ArmorSeal 1000 HS epoxy floor coating product page (Sherwin-Williams)

Next steps for this project

The usual order for a flooring & tile project. See all flooring & tile calculators.

Results are estimates based on standard formulas and typical product specifications. Confirm quantities with your supplier and local code before ordering.