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Epoxy Floor Calculator: Gallons and Kits for a Garage
Work out how much epoxy floor coating you need for a garage, basement or shop floor from the area, coat thickness in mils, the number of coats and the product's solids content.
The epoxy coverage formula
One US gallon spread over 1,604 sq ft makes a layer exactly 1 mil (one thousandth of an inch) thick. That gives the standard coverage formula:
coverage (sq ft per gallon) = 1,604 × solids % ÷ wet mils
A 100% solids epoxy applied at 10 mils covers about 160 sq ft per gallon. A water-based coating that is 50% solids loses half its thickness as it dries, so you need twice the wet thickness to get the same dry film. The calculator adds 10% for the rough, porous surface of concrete and for what stays in the tray.
Worked example: two-car garage
A 20 × 20 ft garage is 400 sq ft. Two coats of 100% solids epoxy at 10 mils need 400 × 2 ÷ 160 = 5 gallons, or 5.5 with 10% extra. That is three 2-gallon kits. A single coat of a typical 40% solids DIY kit at 6 mils covers about 270 sq ft per gallon, so the same garage needs about 1.6 gallons, but the finished film is only 2.4 mils thick and will wear much sooner.
How thick should an epoxy floor be?
| System | Typical total dry thickness |
|---|---|
| Water-based DIY kit (1 coat) | 2 to 4 mils |
| Primer + 100% solids color coat | 10 to 16 mils |
| Full flake system (base, flake, topcoat) | 20 to 30 mils |
| Self-leveling or mortar epoxy (industrial) | 60 to 250 mils |
Surface prep matters more than the coating
- Most epoxy failures are peeling from poor prep. Grind or acid-etch the concrete so it feels like medium sandpaper, then vacuum.
- Do a moisture test: tape a 2 × 2 ft plastic sheet down for 24 hours. Darkened concrete or droplets underneath mean you need a moisture-tolerant primer.
- New concrete should cure at least 28 days before coating.
- Watch the pot life. Mixed 100% solids epoxy can harden in 20 to 30 minutes in the bucket, so pour it out on the floor right after mixing.
Pouring a new garage slab first? Use the concrete calculator.
Frequently asked questions
How much epoxy do I need for a 2-car garage?
A 400 sq ft two-car garage needs about 5.5 gallons of 100% solids epoxy for two 10 mil coats, including 10% extra for porous concrete.
How many square feet does a gallon of epoxy cover?
A gallon of 100% solids epoxy covers about 160 sq ft at 10 mils and about 320 sq ft at 5 mils. Water-based coatings cover more per gallon but leave a thinner dry film.
What does mils mean for epoxy?
A mil is one thousandth of an inch. Coating thickness is given in wet mils (as applied) and dry mils (after the solvent or water evaporates). For 100% solids epoxy the two are the same.