Epoxy mils to coverage: square feet per gallon
100% solids, so wet film equals dry film. A US gallon is 231 cubic inches and covers 1,604 sq ft at 1 mil. For any other product, multiply the coverage by the solids fraction (a 50% solids coating at 10 mils covers 80 sq ft per gallon, not 160). Gallons per 400 sq ft is the raw figure before waste.
| Film thickness | Coverage | Gallons per 400 sq ft | Where it is used |
|---|---|---|---|
| 1 mil | 1,604 sq ft/gal | 0.25 gal | The base figure every other row divides |
| 3 mils | 535 sq ft/gal | 0.75 gal | Water-based garage kit, dry film |
| 5 mils | 321 sq ft/gal | 1.25 gal | Thin roll-on sealer |
| 6 mils | 267 sq ft/gal | 1.50 gal | Light-duty color coat |
| 8 mils | 201 sq ft/gal | 1.99 gal | Polyaspartic topcoat, wet film |
| 10 mils | 160 sq ft/gal | 2.49 gal | Residential garage base coat |
| 12 mils | 134 sq ft/gal | 2.99 gal | High-build shop and warehouse floor |
| 15 mils | 107 sq ft/gal | 3.74 gal | Heavy commercial build |
| 20 mils | 80 sq ft/gal | 4.99 gal | Metallic pour, light |
| 25 mils | 64 sq ft/gal | 6.23 gal | Metallic pour, heavy |
| 30 mils | 53 sq ft/gal | 7.48 gal | Maximum single-pass build |
| 250 mils | 6.4 sq ft/gal | 62.3 gal | Quarter-inch epoxy mortar |
The whole system, garage by garage
Gallons include 10% waste and are the amount needed, not the amount to buy. Round each column up on its own, because these are three separate products. Primer at 200 sq ft per gallon, base coat 100% solids at 10 mils (160 sq ft/gal), clear topcoat at 150 over a full flake broadcast of 0.15 lb per sq ft. Drop the last two columns for a plain solid-color floor.
| Garage | Floor area | Primer | Base coat | Clear topcoat | Flake, full |
|---|---|---|---|---|---|
| 12 × 20 ft (1-car) | 240 sq ft | 1.3 gal | 1.6 gal | 1.8 gal | 36 lb |
| 12 × 22 ft (1-car) | 264 sq ft | 1.5 gal | 1.8 gal | 1.9 gal | 40 lb |
| 20 × 20 ft (2-car) | 400 sq ft | 2.2 gal | 2.7 gal | 2.9 gal | 60 lb |
| 20 × 22 ft (2-car) | 440 sq ft | 2.4 gal | 3.0 gal | 3.2 gal | 66 lb |
| 24 × 24 ft (2-car) | 576 sq ft | 3.2 gal | 4.0 gal | 4.2 gal | 86 lb |
| 32 × 22 ft (3-car) | 704 sq ft | 3.9 gal | 4.8 gal | 5.2 gal | 106 lb |
How much epoxy do I need?
One gallon of coating spread at 1 mil covers 1,604 sq ft, and everything else on this page follows from that.
Divide 1,604 by your target thickness and multiply by the solids fraction. So 100% solids at 10 mils covers 160 sq ft per gallon, and a ~50% solids epoxy paint at 3 mils covers about 267.
A 2-car garage, worked
A 20 × 22 ft garage is 440 sq ft. One 10-mil coat of 100% solids epoxy is 3.0 gallons and a primer coat at 200 sq ft/gal is 2.4, both with 10% waste. They’re different products, though, so you buy 4 of one and 3 of the other, not 6 of something. Add a clear topcoat and it’s 2 more.
That’s partly why 100% solids kits are sold by rated coverage rather than by gallon. A 3 US gal (11.4 L) kit is typically rated around 480–500 sq ft at 10 mils, which is one two-car garage for one coat. Water-based kits are a different animal. Rust-Oleum EpoxyShield ships 240 oz (1.9 gal) rated to 500 sq ft, because it dries to about 3 mils rather than 10.
How many pounds of flake for a full broadcast: 1/8 in vs 1/4 in
Published sources don’t agree on flake broadcast rate, so here’s the spread rather than one tidy figure. Concrete Floor Supply puts a full broadcast of 1/4 in flake at 10 lb per 100 sq ft. That’s 0.10 lb per square foot, or 1 lb per 10 sq ft, though the trade more often quotes 1 lb per 8 to 10 sq ft.
Concrete Floor Supply doubles that for 1/8 in flake, at 20 lb per 100 sq ft, on the reasoning that finer chip packs tighter and so weighs more for the same coverage. Garage Flooring LLC ignores flake size entirely and splits the rule by who’s holding the box: floor area divided by five for a first-timer, divided by six for someone who has done it before. That works out at 0.20 and 0.167 lb per square foot.
Real jobs land in the middle. A Garage Journal thread documenting a full-broadcast floor recorded 320 lb going down on about 2,100 sq ft, which is 0.15 lb per square foot. That’s the figure the full broadcast preset in this epoxy flake calculator uses. Why is the range so wide? Broadcasting to refusal means deliberately over-throwing. You keep flinging chip into the wet base until it stops sinking in, then sweep up and reclaim whatever’s loose the next day. How much comes back depends on how high you throw, how still the air is and how clean the slab was.
Work it as a range rather than a number. Take a 20 x 22 ft two-car garage, 440 sq ft. At 0.10 lb per square foot you need 44 lb, at 0.15 you need 66 lb and at 0.20 you need 88 lb. Flake sells in 25 and 40 lb boxes, so that’s two to four 25 lb boxes depending on which authority you follow.
Running out mid-broadcast is far worse than having a box left over (you can’t pause a wet base coat and drive to the supplier). Buy toward the top of the range if this is your first broadcast or you’ve chosen 1/8 in flake, and toward the middle if you’re using 1/4 in and have done it before.
How many gallons of epoxy do I need for my garage floor: 1, 2 and 3 car
Measure the slab, not the building. Tape the inside face of the walls, back wall to door line, since you’ll coat right to the threshold. If you’re pricing before you measure, a one-car garage is usually 12 x 20 or 12 x 22 ft (240 to 264 sq ft). A two-car is commonly 20 x 22 ft (440 sq ft), with 24 x 24 ft (576 sq ft) the roomier build. A three-car runs around 32 x 22 ft (704 sq ft). Deduct nothing for a fitted workbench unless you really mean to leave the floor beneath it bare. Those small omissions are your waste allowance, not a saving.
The 1,604 this garage floor epoxy calculator runs on isn’t arbitrary. A US gallon is exactly 231 cubic inches. Spread one mil (0.001 in) thick, that covers 231,000 square inches, or 1,604 sq ft.
Divide by your target film, multiply by the solids fraction, and you have the coverage rate for any product. At the residential default (100% solids at 10 mils, so 160 sq ft per gallon) the base coat is straightforward division. The 264 sq ft one-car floor takes 1.65 gal before waste, the 440 sq ft two-car takes 2.75 gal and the 704 sq ft three-car takes 4.4 gal. Add primer at 200 sq ft per gallon and those become 1.32, 2.2 and 3.52 gal.
Add 10% waste across the lot and round up, because epoxy is sold in fixed kit sizes and a part-mixed kit is a wasted kit. So how many gallons of epoxy do you need for your garage floor? Four whole gallons for a one-car, seven for a two-car and nine for a three-car, primer included, counted as separate products (a part-gallon of primer doesn’t turn into base coat).
Sanity-check that against a cost per square foot before ordering. At the $120 per gallon this tool defaults to (US, mid-2026), seven gallons on the two-car floor is $840 of resin, or $1.91 per square foot. That sits inside the $1.50 to $2.50 per square foot that DIY kit materials typically run. Come out well above that and you’ve probably either over-specified the film or double-counted a coat.
Primer, base coat, second coat and topcoat: coverage for each layer
Each layer in the stack has its own coverage rate and they aren’t interchangeable. Primer is a thin, low-viscosity resin whose job is to soak into the slab and seal it, so it spreads far (200 to 250 sq ft per gallon on a smooth troweled floor, dropping to 150 to 200 on a slab that’s just been ground open). This calculator uses 200 sq ft per gallon, which is a fair middle. Thirsty concrete drinks primer and your yield falls. That’s the primer doing its job rather than a fault. Budget for the lower end on any floor you’ve diamond-ground or shot-blasted, whatever the label claims.
The base coat is where mil thickness matters, and it’s also where people quietly forget that two coats means twice the resin. One 10-mil pass of 100% solids epoxy covers 160 sq ft per gallon. A second color coat is another full pass at the same rate, so 440 sq ft becomes 5.5 gal of base rather than 2.75. This epoxy mil thickness calculator prices only the coat you specify, so for a two-coat color build double the result or run the figures twice.
A flake floor rarely needs a second color coat, since the broadcast hides the base entirely. That’s one reason flake systems usually work out cheaper in resin than a solid-color build.
The clear topcoat is the layer most people under-buy, because it goes over texture rather than a flat slab. Over a full flake broadcast a polyaspartic or polyurea topcoat covers roughly 130 to 200 sq ft per gallon depending on the product, since the resin has to flood the gaps between chips before it levels. Over a metallic floor, already smooth, the same product stretches to 200 to 250.
To model a topcoat here, set the thickness so the coverage row lands in that band (10 mils returns 160 sq ft per gallon, which is about right for flake). On the 440 sq ft two-car floor that’s about 3 gal. If you’ve broadcast to refusal, buy toward the low-coverage end.
Metallic epoxy coverage per gallon
Metallic epoxy is the same 1,604 arithmetic run at a much heavier film. Manufacturers scatter widely on where that film should sit. Concrete Floor Solutions quotes 60 to 90 sq ft per gallon. Spartan publishes 70 sq ft per gallon at 22 mils and 53 at 30 mils, figures that sit close to the 100% solids formula without quite landing on it (1,604 divided by 30 gives 53, but 1,604 divided by 22 gives 73, so their 70 is a shade conservative).
EpoxyMaster recommends one gallon per 80 sq ft for the best look. Leggari’s own kit coverages work out at roughly 45 to 67 sq ft per gallon, appreciably thicker than the rest. So the working range for metallic epoxy coverage per gallon is about 45 to 90 sq ft, or 18 to 36 mils. Unlike the flake rate, this isn’t disagreement about one product. These are different products applied at different builds.
To use this epoxy floor coating calculator for a metallic pour, leave the product on 100% solids and set the thickness to match your own data sheet. 20 mils returns 80 sq ft per gallon, 30 mils returns 53. On the 440 sq ft two-car garage that’s the difference between about 5.5 gal and 8.3 gal of metallic resin, a swing of nearly three gallons. At metallic pricing that’s real money, and reason enough to read the sheet rather than a generic chart.
Metallic needs a primer or pigmented base coat under it, because the effect depends on a uniform opaque background. Don’t thin it over bare gray concrete. Price that layer separately, at 200 sq ft per gallon.
Concrete prep, porosity, moisture and slab temperature
No coverage figure survives bad prep. Epoxy bonds mechanically, so the slab has to be opened to a measurable roughness on the ICRI concrete surface profile scale (Guideline 310.2R, running CSP 1 to 10). Published mappings disagree at the edges. Thin sealers are generally placed at CSP 1 to 2, and high-build epoxy anywhere from CSP 3 to 5 depending on whose table you read, with some sources pushing high-build as far as CSP 5 to 6.
What nobody disputes is that acid etching tops out around CSP 1, and at best 2 or 3, which is why the trade has largely abandoned it. A diamond grinder gets you to roughly CSP 2 and a light shot blast to CSP 3. For an 8 to 12 mil garage coat, that’s the territory you want.
Once ground, check porosity, since it drives how much resin the slab drinks. ASTM F3191 is the field method. Place about 0.05 mL of water (a single drop) on the prepped concrete and watch it. Absorbed inside a minute and the floor is porous. Still sitting proud after a minute and it’s non-porous, which on a garage slab usually means a sealer or curing compound is still there and you haven’t ground deep enough. A porous, freshly ground or shot-blasted floor typically takes 5 to 15% more than the chart says, so this calculator defaults to 10% waste. Test three or four spots, since slabs are rarely uniform.
Moisture is what actually delaminates epoxy, and the taped-plastic moisture test is the cheap first screen. ASTM D4263 is the formal version. Tape an 18 x 18 in sheet of polyethylene down on all four edges, leave it a minimum of 16 hours, then lift it and look for condensation on the plastic or a darkened patch on the slab. It’s qualitative only, and it reads surface moisture rather than what’s migrating up through the slab, so a pass is an encouraging sign and not a clearance.
If the floor is below grade, has no vapor barrier or has failed a coating before, pay for the quantitative tests. ASTM F1869 measures vapor emission with anhydrous calcium chloride over 60 to 72 hours, commonly capped at 3 lb per 1,000 sq ft per 24 hours. ASTM F2170 drills probes to 40% of slab depth on a one-sided-drying slab to read internal relative humidity, commonly capped at 75%.
Temperature is the other hard gate. Read the slab with an infrared thermometer, not the air. Most epoxies want concrete between 60 and 90°F (16 to 32°C) and won’t cure reliably below 50°F (10°C).
This is what ends most winter jobs. A cold slab that stalls a cure may never restart when the weather turns. In an unheated garage that 50°F floor rules out roughly November through March across the northern states and most of Canada. Heat the space for 24 to 48 hours beforehand and keep it heated right through the cure. Or drop to a low-temperature epoxy rated to 35 to 50°F, or use a 1-part polyurea workable down to about 40°F (4°C). The test methods above travel. Canadian contractors run the same ASTM and ICRI procedures, with no CSA substitute to swap in.
Common questions
How many gallons for a 2-car garage floor?
For a typical 480 sq ft floor, about 3 gallons per 10-mil coat of 100% solids epoxy, plus ~2.5 gallons of primer. Two color coats doubles the base figure.
How many square feet does a gallon of epoxy cover?
It depends on thickness and solids. 100% solids at 10 mils covers 160 sq ft, while thin epoxy paints claim 250–300 sq ft because they dry to only ~3 mils.
How much flake for a full broadcast?
Broadcast to refusal takes roughly 0.10–0.20 lb per sq ft (1 lb covers 5–10 sq ft). Flakes come in 25 and 40 lb boxes, so a 2-car garage full broadcast needs ~3 × 25 lb boxes.
What does 100% solids mean?
It means no solvent, so the wet film thickness equals the dry film. Solvent-based products shrink as they cure, and their real coverage at a given dry thickness is proportionally lower.
How thick should a garage epoxy coating be?
For the base coat of a residential garage, 8–12 mils is the usual band. Flake systems with a topcoat land around 20–30 mils total.
Should I buy extra for rough concrete?
Yes. Add 5–15% on porous, rough or freshly ground slabs, since they drink more resin. This calculator defaults to 10% waste.
How many gallons of epoxy do I need for my garage floor?
For a 10-mil coat of 100% solids epoxy including primer and 10% waste, it’s about 4 gallons for a 12 x 22 ft one-car garage, 7 for a 20 x 22 ft two-car and 9 for a 32 x 22 ft three-car. Measure your own slab rather than trusting the standard sizes, since real garages vary more than the plans suggest.
Should I use 1/8 in or 1/4 in flake?
Both give full coverage. They differ in look and in quantity. Quarter-inch flake reads as a bold, chunky terrazzo and is usually quoted at about 0.10 lb per square foot at full broadcast. Eighth-inch flake gives a finer, more uniform speckle and packs tighter, so some suppliers double the rate to 0.20 lb per square foot. Budget the higher figure for the smaller chip.
Do I need two coats of epoxy?
Only on solid-color floors. A second color coat doubles your base-coat resin (440 sq ft goes from 2.75 to 5.5 gallons at 160 sq ft per gallon), but it evens out the patchiness a single pass leaves over gray concrete. Flake floors rarely need it, because a full broadcast hides the base entirely.
Is polyaspartic or epoxy better for the topcoat?
They do different jobs. Epoxy is the build coat, with high solids, a thick film and a strong mechanical bond to concrete. Polyaspartic and polyurea are topcoats (faster curing, better UV and chemical resistance, less prone to yellowing). Most flake systems run epoxy underneath and polyaspartic over the top at roughly 130 to 200 sq ft per gallon over the flake texture. This calculator plans on 150.
Do I have to grind the concrete, or can I acid etch?
Grind if you possibly can. Acid etching reaches only about CSP 1 on the ICRI profile scale, and 2 or 3 at absolute best, and it does nothing at all to a sealed or hard-troweled slab. A diamond grinder gets you to roughly CSP 2 and a light shot blast to CSP 3, which is what an 8 to 12 mil garage coating wants underneath it.
How much does an epoxy garage floor cost per square foot?
In the US as of mid-2026, DIY materials run about $1.50 to $2.50 per square foot, or $2 to $5 for a complete DIY build once flake and topcoat are in. Professionally installed it’s $3 to $12 per square foot, with most residential garages landing at $5 to $7 and metallic systems at $9 to $15. Divide this calculator’s cost figure by your floor area to compare, and check your local supplier before you commit.
Can I epoxy a garage floor in winter?
Only if you can warm the slab and keep it warm. Most epoxies want the concrete between 60 and 90°F (16 to 32°C) and won’t cure reliably below 50°F (10°C). Read the slab with an infrared thermometer, not the air. Heat the space for 24 to 48 hours first and hold it through the full cure, or switch to a low-temperature epoxy rated to 35 to 50°F or a 1-part polyurea workable to about 40°F (4°C). In an unheated garage the temperature floor rules out roughly November through March across the northern states and most of Canada, and a cure that stalls in the cold may not restart when the weather turns.
How do I convert mils to square feet per gallon?
Divide 1,604 by the mils, then multiply by the solids fraction. A US gallon is 231 cubic inches by definition, and spread 0.001 in thick that volume covers 231,000 square inches, which is 1,604 sq ft. So 100% solids at 10 mils is 160 sq ft per gallon and at 12 mils is 134. For 100% solids there’s a shortcut worth memorizing. Gallons per 400 sq ft equals the mils divided by four.
What is the difference between wet film thickness and dry film thickness?
Wet film is dry film divided by the solids fraction. At 100% solids the two are identical, so a 10 mil target is 10 mils on the gauge. At 48% solids a 3 mil dry film needs 6.3 mils wet. Manufacturers publish application rates in wet mils because that’s what you measure while rolling (Ghostshield Polyaspartic 980 quotes 150–200 sq ft per gallon at 8 mils wet film). Coverage charts are dry film, so check which you have before ordering.
How much clear topcoat do I need over a flake floor?
For a 20 × 22 ft garage (440 sq ft), about 3.2 gallons, bought separately from the base coat. A full broadcast drops polyaspartic coverage to roughly 150 sq ft per gallon, since the resin has to flood the gaps between chips before it levels. The same product over a smooth solid color coat stretches to 250–300 sq ft per gallon. On a flake system it’s the biggest resin line on the job, bigger than the base coat it covers.
Does the primer count toward my epoxy gallons?
No. Primer is a separate product with its own coverage rate, can and price, so round it up on its own. A 440 sq ft two-car garage takes about 2.4 gallons of primer at the 200 sq ft per gallon this calculator assumes and about 3.0 gallons of 100% solids base coat at 10 mils. Add those to 5.4 and buy 6 gallons of anything and you’re short of both. Order four separate lines for a flake floor: primer, base, flake, topcoat.
Why does a 2 gallon epoxy kit say it covers 500 square feet?
It’s a thin water-based coating, not a 100% solids build. The Rust-Oleum EpoxyShield 2.5-car kit holds 240 fl oz (1.875 gallons), rated up to 500 sq ft in one coat. It works out at 267 sq ft per gallon, or roughly 3 mils dry at about 48% solids. A 100% solids kit rated to the same 500 sq ft holds three gallons, because 10 mils takes 160 sq ft per gallon. Same floor, same claim on the box, three times the film.