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

A 20 × 20 ft two-car garage is 400 sq ft. With 10% waste that is 440 sq ft, which is 2 of the water-based 1-car kits (each sold as covering up to 250 sq ft) or 1 of the 2.5-car kits (up to 500 sq ft) in one coat. A 100% solids kit of 1.5 gal at 10 mils a coat needs 2. Change the product, coats and waste in the calculator to see yours.

How many square feet does a gallon of epoxy cover?

It depends on how thick you put it on. One US gallon of any coating spreads over 1,604 sq ft one mil (0.001 in) thick, so a 100% solids epoxy at 10 mils a coat covers about 160 sq ft per gallon, and at 16 mils about 100. Makers’ practical figures are lower than the geometry because some epoxy stays in the pail and concrete soaks some up: ArmorPoxy, for instance, lists 115 to 170 sq ft per gallon at 8 to 12 mils. Water-based epoxy is partly water, so use the kit’s own coverage instead.

How many coats of epoxy does a garage floor need?

Rust-Oleum’s EpoxyShield kit is applied in one coat by its instructions. Professional systems with 100% solids epoxy are often a base coat of 8 to 12 mils, a broadcast of color flakes and one or two clear topcoats. Each extra coat needs its own coverage, so the kit count goes up in proportion; set the number of coats and, for 100% solids, the mils per coat.

Why does the calculator suggest 25% extra on rough concrete?

Coverage figures are for smooth, sound concrete. Rust-Oleum itself gives a lower figure for rough, porous concrete (roughly 125 to 200 sq ft per 120 oz kit instead of 250), so the "up to" kit count can be short by up to half on a worn floor. The 25% setting is a rule-of-thumb allowance, not a published figure; if your floor is very rough or has never been sealed, round up another kit.

How long should new concrete cure before epoxy?

Coatings makers commonly ask for at least 28 days of cure on new concrete, and the slab should pass a moisture check first, for instance the plastic sheet test (ASTM D4263): tape a sheet to the floor for 16 to 24 hours and look for moisture underneath. Follow your product’s instructions, which override this general guidance.

Are the kit sizes the same everywhere?

No. This calculator uses Rust-Oleum EpoxyShield garage floor kits (120 and 240 fl oz) and a 1.5 gal 100% solids kit as examples. Other brands change their kit sizes and coverage, so check the label and, if it differs, work out the kits yourself: area with waste × coats ÷ the coverage per kit per coat.

Should I round up the number of kits?

Yes. Epoxy is mixed in whole kits with a limited working time, and a part-kit cannot be bought. Running out half-way across a floor leaves a lap line. If your result is just over a whole number, buy the extra kit for edges and cracks.

Epoxy Floor Coating Calculator

Kits of epoxy = floor area × (1 + waste) × coats ÷ the area one kit covers per coat, rounded up. A 20 × 20 ft two-car garage is 400 sq ft, or 440 sq ft with 10% waste: 2 kits of a water-based 1-car epoxy kit (sold as covering up to 250 sq ft in one coat), or 1 of the 2.5-car kit (up to 500 sq ft). With a 1.5 gal 100% solids kit at 10 mils a coat, that is 2 kits (3 gal), because one gallon covers 1,604 sq ft ÷ mils. Coverage figures are the makers’ best case and the film-thickness math is theory: treat the count as an estimate.

Figures based on the sources listed belowUpdated 2026-10-07How we calculate

Floor length

Floor width

Waste allowance

Exact (0%)Standard (+10%)Rough or porous concrete (+25%)Custom

ProductThe water-based kit sizes use the maker’s "up to" coverage on smooth concrete. 100% solids kits are worked from the film thickness you choose.

Coats

The water-based kit is applied in one coat by its instructions; a second coat needs a second set of coverage. For 100% solids, the mils below are per coat.

Price per kit (optional)

Buy 2 kits

400 sq ft + 10% waste = 440.00 sq ft

Coating you buy: 1.9 gal, mixed, all kits
Coverage used (area with waste × coats): 440 sq ft (of 500 sq ft)

Low

$140.00

Expected

$200.00

High

$280.00

Includes 40.00 sq ft waste

How this number is calculated

400 sq ft + 10% waste = 440.00 sq ft ÷ 250 sq ft per kit = 2 kits

Shopping list

Garage floor epoxy kit
Concrete etch or degreaser
Epoxy roller cover (3/8 in nap) and extension pole
Decorative color flakes
Spiked shoes for wet epoxy

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How many epoxy kits for common floors

Worked by this calculator: one coat, 10% waste, rounded up. Water-based kits at the makers’ up-to coverage (250 and 500 sq ft); 100% solids is a 1.5 gal kit at 10 mils a coat (about 240 sq ft). Rough or porous concrete needs more.
Floor	Area with waste (sq ft)	1-car kits (250 sq ft)	2.5-car kits (500 sq ft)	100% solids kits (1.5 gal, 10 mils)
10 × 20 ft (single-bay, one side)	220	1	1	1
12 × 20 ft (1-car garage)	264	2	1	2
20 × 20 ft (2-car garage)	440	2	1	2
24 × 24 ft (large 2-car garage)	633.6	3	2	3
30 × 30 ft (3-car garage)	990	4	2	5
20 × 30 ft (basement)	660	3	2	3

Coverage of 100% solids epoxy by film thickness

Theoretical coverage, 1,604 sq ft per gallon ÷ mils, for a perfectly smooth sealed floor with nothing left in the pail. One mil is 0.001 in. Real floors cover less; the calculator’s waste setting makes up the difference.
Thickness per coat	Sq ft per gallon	Sq ft per 1.5 gal kit
4 mils	401	602
6 mils	267	401
8 mils	201	301
10 mils	160	241
12 mils	134	201
16 mils	100	150
20 mils	80	120

Methodology & assumptions

Floor area is length times width, less any area you will not coat. The area is multiplied by 1 plus the waste allowance (0%, 10% or 25%) and by the number of coats, then divided by the area one kit covers in a single coat, and rounded up to whole kits. For the water-based kits that coverage is the maker’s up-to figure on smooth concrete: 250 sq ft for the 120 fl oz 1-car kit and 500 sq ft for the 240 fl oz 2.5-car kit (Rust-Oleum EpoxyShield). For 100% solids epoxy, one US gallon covers 1,604 sq ft at a thickness of one mil, so a kit’s coverage per coat is its gallons × 1,604 ÷ the mils per coat: a 1.5 gal kit at 10 mils is about 240.6 sq ft per coat. That is a theoretical figure for a smooth, sealed floor; in practice some epoxy stays in the pail and a porous floor soaks some up, which the 25% option is meant to cover (it is a rule of thumb, not a published rate). Kit sizes, the 1.5 gal 100% solids kit and the price ranges are typical, not any brand’s catalog. Prices are unverified typical ranges and can be overridden in the calculator. The metric toggle shows the floor in m and coverage in m²; kits stay in the sizes sold in the US.

Rust-Oleum, EpoxyShield Garage Floor Coating product page: 1-car kit (120 fl oz) up to 250 sq ft, 2.5-car kit (240 fl oz) up to 500 sq ft
Rust-Oleum, EpoxyShield technical data sheets (ESH-09 water-based epoxy garage floor coating; ESH-39 pouch kits): application and coverage on smooth and porous concrete
Duraamen, Coatings Coverage Chart: 1,604 sq ft per gallon at 1 mil; 100% solids at 10 dry mils is about 160 sq ft per gallon
ArmorPoxy, 100% solids epoxy product literature: practical coverage 115 to 170 sq ft per gallon at 8 to 12 mils; 1.5 gal kit (1 gal Part A + 0.5 gal Part B) covers 200 to 300 sq ft
Sherwin-Williams, How Soon Can You Epoxy Coat Freshly Poured “Green” Concrete?: 28-day cure guidance for new concrete
ASTM D4263, Standard Test Method for Indicating Moisture in Concrete by the Plastic Sheet Method
Typical US epoxy floor kit retail price ranges (unverified estimate)

How to calculate how much epoxy a floor needs

Measure the floor. Measure the length and width of the floor in feet and multiply them. Subtract anything you will not coat, such as a drain pad or a built-in workbench.
Pick the product. Choose the water-based 1-car or 2.5-car kit, or a 100% solids kit. For 100% solids, set the thickness in mils of each coat.
Set the coats. Enter the number of coats. The water-based kit is applied in one coat; each additional coat needs its own coverage.
Add waste for porous concrete. Add 10% for edges and spills, or 25% for rough or porous concrete that soaks up more than the label figure.
Divide by kit coverage and round up. Multiply the area with waste by the number of coats, divide by the area one kit covers per coat, and round up to whole kits.

Worked examples

Project	Result
20 × 20 ft two-car garage, 1-car kits, one coat, 10% waste	400 sq ft + 10% waste ≈ 440 sq ft → 2 kits
24 × 24 ft garage, 2.5-car kits, one coat, 10% waste	576 sq ft + 10% waste ≈ 633.6 sq ft → 2 kits
20 × 20 ft garage, 100% solids base coat at 10 mils, 10% waste	400 sq ft + 10% waste ≈ 440 sq ft → 2 kits
20 × 30 ft rough basement floor, 1-car kits, two coats, 25% waste	600 sq ft + 25% waste ≈ 750 sq ft → 6 kits

Frequently asked questions

How much epoxy do I need for a 2-car garage floor?: A 20 × 20 ft two-car garage is 400 sq ft. With 10% waste that is 440 sq ft, which is 2 of the water-based 1-car kits (each sold as covering up to 250 sq ft) or 1 of the 2.5-car kits (up to 500 sq ft) in one coat. A 100% solids kit of 1.5 gal at 10 mils a coat needs 2. Change the product, coats and waste in the calculator to see yours.
How many square feet does a gallon of epoxy cover?: It depends on how thick you put it on. One US gallon of any coating spreads over 1,604 sq ft one mil (0.001 in) thick, so a 100% solids epoxy at 10 mils a coat covers about 160 sq ft per gallon, and at 16 mils about 100. Makers’ practical figures are lower than the geometry because some epoxy stays in the pail and concrete soaks some up: ArmorPoxy, for instance, lists 115 to 170 sq ft per gallon at 8 to 12 mils. Water-based epoxy is partly water, so use the kit’s own coverage instead.
How many coats of epoxy does a garage floor need?: Rust-Oleum’s EpoxyShield kit is applied in one coat by its instructions. Professional systems with 100% solids epoxy are often a base coat of 8 to 12 mils, a broadcast of color flakes and one or two clear topcoats. Each extra coat needs its own coverage, so the kit count goes up in proportion; set the number of coats and, for 100% solids, the mils per coat.
Why does the calculator suggest 25% extra on rough concrete?: Coverage figures are for smooth, sound concrete. Rust-Oleum itself gives a lower figure for rough, porous concrete (roughly 125 to 200 sq ft per 120 oz kit instead of 250), so the "up to" kit count can be short by up to half on a worn floor. The 25% setting is a rule-of-thumb allowance, not a published figure; if your floor is very rough or has never been sealed, round up another kit.
How long should new concrete cure before epoxy?: Coatings makers commonly ask for at least 28 days of cure on new concrete, and the slab should pass a moisture check first, for instance the plastic sheet test (ASTM D4263): tape a sheet to the floor for 16 to 24 hours and look for moisture underneath. Follow your product’s instructions, which override this general guidance.
Are the kit sizes the same everywhere?: No. This calculator uses Rust-Oleum EpoxyShield garage floor kits (120 and 240 fl oz) and a 1.5 gal 100% solids kit as examples. Other brands change their kit sizes and coverage, so check the label and, if it differs, work out the kits yourself: area with waste × coats ÷ the coverage per kit per coat.
Should I round up the number of kits?: Yes. Epoxy is mixed in whole kits with a limited working time, and a part-kit cannot be bought. Running out half-way across a floor leaves a lap line. If your result is just over a whole number, buy the extra kit for edges and cracks.

Handy tools

Feet and Inches Calculator: Add up garage wall lengths measured in feet, inches and fractions, and get the decimal feet for the fields above.