Epoxy flake calculator
Pounds and boxes of flake for the broadcast between base and topcoat.
Free tool
Epoxy coverage calculator
How much epoxy to buy for a floor: kits and gallons for every coat, and what they cost. Answer two quick questions; mils, solids and kit sizes are already filled in, and you can fine-tune them.
The formula
Epoxy floor coverage: how the calculator works
Coverage is worked out the same way across the coatings industry. A US gallon is 231 cubic inches; spread 1 mil (0.001 inch) thick, it covers 1,604 sq ft. Only the solids stay on the floor, so:
- Spread rate (sq ft per gallon) = 1,604 × volume solids ÷ dry film thickness (mils).
- Wet film thickness = dry film thickness ÷ volume solids, which is the same as 1,604 ÷ spread rate.
- Gallons = area ÷ spread rate, plus the first-coat allowance on the first coat, plus waste.
- Kits = gallons ÷ kit size, rounded up for each coat. Two-part products should be mixed as full kits, so the calculator never splits one.
Worked example: a 400 sq ft flake floor
- Primer, 100% solids at 4 mils: 1,604 ÷ 4 = 401 sq ft per gallon. 400 ÷ 401 = 1.00 gal, × 1.10 first-coat allowance × 1.10 waste = 1.21 gal: one 1.5-gal kit, $123.75.
- Base coat, 100% solids at 10 mils: 160.4 sq ft per gallon. 400 ÷ 160.4 = 2.49 gal × 1.10 = 2.74 gal: one 3-gal kit, $159.
- Polyaspartic topcoat at 130 sq ft per gallon: 400 ÷ 130 = 3.08 gal × 1.10 = 3.38 gal: two 2-gal kits, $411. At 91.5% solids that leaves about 11.3 dry mils.
- Total: 7.3 gal needed, 8.5 gal bought in 4 kits, $693.75, or $1.73 a square foot before flake.
The formula gives theoretical coverage on a smooth surface with nothing lost. Real coverage depends on the slab's profile and porosity, how the coat is applied, the crew and the weather, which is what the waste and first-coat lines are for: raise them for rough or very thirsty slabs.
Use the data sheet for your product. Volume solids, the film thickness range and the kit size are all on the technical data sheet; when a rule of thumb and the data sheet disagree, follow the data sheet. Every term is explained in the glossary.
The three systems
| System | Coats (typical) |
|---|---|
| Standard garage flake | Primer 3–8 mils · base coat 8–12 mils with a full flake broadcast · clear topcoat at 100–160 sq ft per gallon |
| Heavier double broadcast | As above, plus a second base coat of 12–16 mils and a second broadcast before the topcoat |
| Solid-color epoxy | Primer 3–8 mils · one body coat of 10–30 mils; a topcoat is optional |
The calculator uses the middle of each range. Flake quantities come from the flake calculator.
100% solids: spread rate by thickness
| Film thickness | Sq ft per gallon | Gallons per 400 sq ft |
|---|---|---|
| 3 mils | 534.7 | 0.75 |
| 4 mils | 401.0 | 1.00 |
| 5 mils | 320.8 | 1.25 |
| 8 mils | 200.5 | 2.00 |
| 10 mils | 160.4 | 2.49 |
| 12 mils | 133.7 | 2.99 |
| 16 mils | 100.3 | 3.99 |
| 20 mils | 80.2 | 4.99 |
| 30 mils | 53.5 | 7.48 |
| 40 mils | 40.1 | 9.98 |
Theoretical, before waste: 1,604 ÷ mils. Multiply by the volume solids for products under 100% solids.
Defaults
How we set the defaults
| Input | Default | Why |
|---|---|---|
| Floor size | 400 sq ft | An example: a 20 × 20 ft garage. Enter your own floor. |
| Primer | 4 mils, 1.5 gal, $123.75 | A tight, thin coat inside the typical 3–8 mils of a 100% solids primer, at a typical listed price for a 1.5-gallon kit. |
| Base coat | 10 mils, 3 gal, $159 | The middle of the typical 8–12 mils under flake (20 mils for solid color, the middle of 10–30), at a typical price for a 3-gallon kit of 100% solids epoxy. |
| Second base coat | 14 mils | The middle of the typical 12–16 mils for a double broadcast. Off for the other systems. |
| Topcoat | 130 sq ft/gal, 91.5%, 2 gal, $205.50 | The middle of the typical 100–160 sq ft per gallon over a full broadcast and 90–93% solids for a polyaspartic, at a typical price for a 2-gallon kit. |
| Waste | 10% | An allowance for material left in buckets and on tools. Change it to match your jobs. |
| Extra for the first coat | 10% | An allowance for bare concrete soaking up the first coat. Raise it for porous or heavily profiled slabs. |
Prices vary by brand and supplier and change over time; use your own.
Questions
Epoxy coverage: frequently asked questions
How do you calculate epoxy coverage?
Divide 1,604 by the dry film thickness in mils and multiply by the volume solids: that is the theoretical square feet per gallon. Divide the floor area by it to get gallons, then add waste and round up to whole kits. A 100% solids epoxy at 10 mils covers 1,604 × 1.00 ÷ 10 = 160 sq ft per gallon.
How many square feet does a gallon of epoxy cover?
A gallon of 100% solids epoxy covers about 1,604 sq ft at 1 mil, so about 160 sq ft at 10 mils and 80 sq ft at 20 mils, before waste. A product with lower volume solids covers less at the same dry thickness, and porous or rough concrete takes more.
How much epoxy do I need for a two-car garage?
For a 400 sq ft floor with the standard garage flake system (primer, base coat, flake and a clear topcoat), about 7.3 gallons of coating: one 1.5-gallon primer kit, one 3-gallon base coat kit and two 2-gallon topcoat kits, including 10% waste and 10% extra on the first coat.
What is the difference between wet and dry film thickness?
Wet film thickness is what you spread; dry film thickness is what is left once any solvent or water has gone. Dry = wet × volume solids, so for a 100% solids epoxy they are the same, and a 90% solids coating needs about 11 wet mils to leave 10 dry.
Why does the first coat on bare concrete take more material?
Freshly ground concrete is porous and soaks up part of the first coat, which is why primer spread rates are given as wide ranges. The calculator adds 10% to the first coat by default; you can change it under “Fine-tune the numbers”.
Cure time, temperature and humidity
Recoat windows, dew point and when the floor can take traffic.
Epoxy flooring supplies
What you will buy for each job and where contractors buy it.
The Epoxy Playbook
Full installations recorded start to finish that you can replay, plus pricing, quoting and selling the job. Required before the hands-on class.
Watch every step before you do it
The Epoxy Playbook: full installations recorded start to finish, which you can replay as often as you need, plus pricing, quoting and selling the job.