Understanding your result
The headline is the number of kits, and the sub-line adds the flake bags and the topcoat. The three figures show the floor area, the flakes for the broadcast you chose and the topcoat.
The table shows the area, the kits with the exact fraction they come from, the flakes needed, the flakes included in the kits, the extra bags, the topcoat with its cans and the cost of the kits. The arithmetic panel shows the division by the box’s coverage and the flake rate.
The kit coverage on the box is the number to check. “2-car” kits vary between brands from about 400 to 500 square feet, and some list coverage for one coat at a thickness that is thin for a garage. The concrete floor calculator covers one-part epoxy paints and sealers; the drying and recoat calculator gives the waits between the base coat and the topcoat; and the porch floor calculator is the one for outdoor slabs.
How we calculate this
Kits are rounded up because a part kit cannot be bought, and a kit once mixed must be used. The broadcast rates are typical figures from decorative-flake suppliers’ guidance for light, medium and full coverage, rounded; a full broadcast covers the base coat completely and the excess is swept up and reused or discarded. The topcoat coverage of 300 sq ft per gallon is typical of clear epoxy and polyaspartic topcoats for garage floors; check your product. The coverage rates table lists floor coatings with the paints.
The prep and the moisture test come from the coating makers’ instructions and ASTM D4263, and the cure times guide explains why a two-part epoxy is walkable in a day but should not see a car for several.
The assumptions behind the numbers
| Assumption | Default | Where it comes from |
|---|---|---|
| Kit coverage | 250 sq ft per coat (23 m²) | Typical “1-car” DIY kit box figure; “2-car” kits about 400–500 |
| Base coats | 1 | Most DIY kits are rated for one coat on a prepared slab |
| Flakes | 2 / 8 / 18 lb per 100 sq ft | Typical decorative-flake supplier guidance for light, medium and full broadcast, rounded |
| Flakes in each kit | 1 lb | A typical included bag |
| Flake bag | 10 lb (5 kg) | A common bulk bag size |
| Clear topcoat | 300 sq ft per gallon + 5% | Typical clear epoxy and polyaspartic topcoat figures |
| Kit price | $120 | A typical 2025 DIY kit price |
Assumptions last reviewed October 8, 2026.
The calculator does not model grinding, crack repair, primer coats under the epoxy, or the professional systems (100% solids epoxy, polyaspartic) that are sold by the gallon and applied at specified mils. For those, the spread rate calculator works from volume solids and film thickness.
Two worked examples
A two-car garage with a light speckle
24 × 20 ft, 250 sq ft kits at $120, one coat, light flakes, clear topcoat.
- Kits: 480 ÷ 250 = 1.92, so 2 kits, $240
- Flakes: 4.8 × 2 = 9.6 lb; 2 lb in the kits, so one 10 lb bag
- Topcoat: 480 ÷ 300 × 1.05 = 1.68 gallons, a gallon and three quarts
The flakes in the kits alone would give a very sparse speckle on a floor this size; the extra bag is what most people expect from the photos on the box.
A full-broadcast floor with two base coats
Same garage, 500 sq ft kits at $200, two base coats, full broadcast.
- Kits: 480 ÷ 500 × 2 = 1.92, so 2 kits, $400
- Flakes: 4.8 × 18 = 86.4 lb; 2 lb in the kits, so nine 10 lb bags
- Topcoat: 1.68 gallons
A full broadcast is a different floor: the flakes are the surface, and the topcoat is what you walk on. A 30 × 24 ft floor with no flakes and no topcoat needs three 250 sq ft kits.
Where to find your inputs
Floor size. Length and width of the slab to be coated.
Kit coverage. On the box, usually “covers up to” so many square feet per kit; use that figure per coat.
Coats. From the kit instructions.
Flakes. Look at photos of floors you like: a scatter is light, half covered is medium, solid colour from flakes is full.
Topcoat. Its can gives the coverage.
Common mistakes
- Mixing two kits at once. The second goes off in the bucket.
- Trusting “2-car” on the box. Check the square feet; garages vary.
- Skipping the moisture test. Epoxy over a damp slab blisters.
- Too few flakes. The kit’s bag is a sample.
- No topcoat over flakes. Loose flakes catch dirt and wear through.
- Driving on it in a day. Walkable is not cured; wait the time on the box.
Questions people ask
- How many epoxy kits do I need for a 2-car garage?
- A 24 × 20 ft garage is 480 sq ft. Kits rated at about 250 sq ft per coat need 1.92, so two kits for one coat, or four for two coats. Kits rated at about 500 sq ft need one for one coat, two for two.
- How many flakes do I need?
- It depends on the look. A light speckle is about 2 lb per 100 sq ft, a medium broadcast about 8 lb and a full broadcast, thrown until the epoxy will take no more, about 18 lb. Most kits include a small bag of about a pound, which covers a light speckle on a small floor only.
- Do I need a clear topcoat?
- On a flake floor, yes, because it locks the flakes in, gives an even gloss and takes the wear. On a solid-colour floor it adds durability and stain resistance. Clear topcoats cover about 300 sq ft per gallon; the calculator adds a 5% allowance.
- What is pot life?
- The time a mixed kit stays workable, typically one to two hours and less in heat. Mix one kit at a time, pour it in ribbons and roll it out immediately; a bucket of mixed epoxy left standing gets hot and sets.
- Should I do one coat or two?
- One coat on a smooth, well-prepared slab with a kit rated for one coat; two on rough or porous concrete, or with the thinner water-based kits, which can look patchy in one coat. A primer coat does the same job as a first coat on porous slabs.
- What prep does an epoxy floor need?
- Degreasing, then etching or grinding to a profile, then vacuuming, and a moisture test with a taped plastic sheet (ASTM D4263) before opening a kit. Epoxy will not bond to a dusty, oily or damp slab.