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

For a 400 square foot double garage, two coats of a 65 percent solids epoxy at 3 mils dry works out at about 2.3 US gallons, roughly 8.7 litres. The same floor in a 100 percent solids product at 10 mils dry needs about 5.3 gallons, roughly 20 litres, because you are laying down more than three times the film. Neither figure includes what stays in the pail and on the roller, so buy the next size up rather than the exact number.

What is a mil, and why does it change the answer so much?

A mil is a thousandth of an inch, about 25 microns, and it is the thickness of the coating once it has dried. Coverage is inversely proportional to it: Sherwin-Williams publishes 1,040 square feet per gallon at one mil for ArmorSeal 1000 HS, so at 3 mils a gallon covers about 347 square feet and at 5 mils about 208. Double the thickness, halve the coverage. It is the single biggest variable in the calculation and the one most online answers silently pick for you.

Does a porous slab really need more product?

Yes, and Benjamin Moore says so without putting a number on it. The Corotech V430 sheet gives 100 to 150 square feet per gallon and adds "Depending on surface texture and porosity". That is why this calculator returns a range across the recommended thickness rather than one figure with a porosity allowance baked in: a thirsty, freshly ground slab finishes at the thick end of the range and a smooth sound one at the thin end. Nobody publishes a percentage for this, so nothing here invents one.

Why does the answer come in gallons when I buy litres?

Because the data sheets are written by American manufacturers and quote square feet per US gallon. The calculator converts for you: a US gallon is 3.785411784 litres exactly, which is not the same as an imperial gallon at 4.546 litres. If a coverage figure you find elsewhere seems 20 percent generous, check which gallon it means. Every litre figure on this page comes from the US gallon.

Should I add extra for waste?

Buy up, do not calculate up. These are theoretical coverage rates, meaning they assume every drop that leaves the pail ends on the floor at the stated thickness. In practice some stays in the pail, some in the tray, some on the roller sleeve you throw away, and a two-part epoxy has a pot life measured in hours so you cannot mix a top-up later at leisure. Sherwin-Williams gives 30 minutes of sweat-in time and 4 hours of pot life at 25C on ArmorSeal 1000 HS. Round up to the next kit rather than adding a percentage you made up.

Can I use these rates for a different brand?

Only if that brand publishes its own volume solids and recommended film thickness, and you use those instead. Coverage is a property of a specific formulation: a 100 percent solids epoxy lays down roughly one and a half times the film of a 65 percent solids one from the same volume, because the difference is solvent that evaporates. Take the theoretical coverage from your own product's data sheet and this page's arithmetic still works. Take it from a different product and the number is fiction.

How Much Epoxy Do You Need?

Last updated: August 26, 2026By EpoxyFloorIndex Research Team

Multiply the floor area by the dry film thickness you are aiming for, then divide by the coverage the manufacturer publishes at one mil. Two coats of a 65 percent solids epoxy at 3 mils on a 400 square foot garage is about 8.7 litres; the same floor in a 100 percent solids product at 10 mils is about 20. The calculator does that against two real data sheets and shows the sentence each rate came from.

How much epoxy will the floor take?

Floor area (sq ft)

Which product are you costing?

Sherwin-Williams ArmorSeal 1000 HSHigh-solids polyamide epoxy, 65% volume solids1,040sq ft/gal at 1 mil · recommended 3 to 5 mils dryBenjamin Moore Corotech V430100% solids self-levelling epoxy floor coating1,500sq ft/gal at 1 mil · recommended 10 to 15 mils dry

Dry film thickness (mils)This sheet recommends 3 to 5 mils dryNumber of coatsEach coat covers the whole floor again

400 sq ft · 2 coats · 3.0 mils dry

8.7 L

2.31 US gallons

Coverage at 3.0 mils1,040 sq ft/gal at 1 mil, divided by the thickness: 347 sq ft/gal
Thin end of the recommended range3.0 mils, a smooth sound slab: 8.7 L
Thick end of the recommended range5.0 mils, a porous or textured slab: 14.6 L

Coverage rate from Sherwin-Williams ArmorSeal 1000 HS product data sheet, revised August 10, 2021: “Theoretical coverage sq ft/gal (m2/L) @ 1 mil / 25 microns dft: 1040 (25.5)” Gallons are US gallons, 3.785 L. This is theoretical coverage, so it makes no allowance for what stays in the pail, on the roller or in the tray.

The data sheets, quoted

A coverage rate is a property of a formulation, not of a market, which is why these come from manufacturers rather than from GTA applicators. Both sheets were downloaded and read in full (August 2026); the sentence carrying each figure is reproduced here so you can check it against whatever is going on your own floor.

Sherwin-Williams ArmorSeal 1000 HS

High-solids polyamide epoxy, 65% volume solids

Volume solids: colors 65% +/- 2%, clear 61% +/- 2%
Coverage at 1 mil dry: 1,040 sq ft/galstated on the sheet
Recommended dry film: 3 to 5 mils
Coverage across that range: 206 to 350 sq ft/gal

“Recommended Spreading Rate per coat: Dry mils 3.0 (75) to 5.0 (125); ~Coverage sq ft/gal (m2/L) 206 (5.0) to 350 (8.6)”

Sherwin-Williams ArmorSeal 1000 HS product data sheet, revised August 10, 2021

Benjamin Moore Corotech V430

100% solids self-levelling epoxy floor coating

Volume solids: Component A 96% +/- 1.0%, Component B 99.7%
Coverage at 1 mil dry: 1,500 sq ft/galarithmetic on two stated figures
Recommended dry film: 10 to 15 mils
Coverage across that range: 100 to 150 sq ft/gal

“Recommended Film Thickness - Wet 10 - 15 mils - Dry 10 - 15 mils. Depending on surface texture and porosity. Be sure to estimate the right amount of paint for the job.”

This sheet does not print a per-mil theoretical coverage. 1500 is the product of two figures it does print: 150 sq ft/gal at the 10 mil end and 100 sq ft/gal at the 15 mil end both give 1500 sq ft x mil per gallon. That is arithmetic on stated numbers, not an estimate.

Benjamin Moore Corotech V430 technical data sheet, M72 V430 EN 080318

What the calculator deliberately does not do

It does not add a waste allowance. Every percentage you see quoted for that online is somebody's habit rather than a published figure, and a made-up 15 percent looks exactly like a measured one once it is printed next to a real coverage rate. What actually happens is that a two-part epoxy has a pot life, so you cannot mix a small top-up an hour later at your convenience. The right response is to buy the next kit size up, not to inflate the arithmetic.

It does not model primer, and a bare or freshly ground slab usually wants one. A primer coat is a separate product with its own coverage rate; run it through the calculator on its own sheet rather than folding it into the topcoat number.

It does not know about flake. A broadcast flake floor is base coat, chips and a clear top coat, and the chips are sold by weight per square foot rather than by film thickness. If you are pricing a flake kit, the base and the clear are what this page estimates and the chips are a separate line.

Finally, it assumes the floor is a floor. A cove base turning up the wall, a stairwell or an equipment plinth all add coated area that a length-times-width measurement never sees.

Frequently asked questions

How much epoxy do I need for a 2 car garage?: For a 400 square foot double garage, two coats of a 65 percent solids epoxy at 3 mils dry works out at about 2.3 US gallons, roughly 8.7 litres. The same floor in a 100 percent solids product at 10 mils dry needs about 5.3 gallons, roughly 20 litres, because you are laying down more than three times the film. Neither figure includes what stays in the pail and on the roller, so buy the next size up rather than the exact number.
What is a mil, and why does it change the answer so much?: A mil is a thousandth of an inch, about 25 microns, and it is the thickness of the coating once it has dried. Coverage is inversely proportional to it: Sherwin-Williams publishes 1,040 square feet per gallon at one mil for ArmorSeal 1000 HS, so at 3 mils a gallon covers about 347 square feet and at 5 mils about 208. Double the thickness, halve the coverage. It is the single biggest variable in the calculation and the one most online answers silently pick for you.
Does a porous slab really need more product?: Yes, and Benjamin Moore says so without putting a number on it. The Corotech V430 sheet gives 100 to 150 square feet per gallon and adds "Depending on surface texture and porosity". That is why this calculator returns a range across the recommended thickness rather than one figure with a porosity allowance baked in: a thirsty, freshly ground slab finishes at the thick end of the range and a smooth sound one at the thin end. Nobody publishes a percentage for this, so nothing here invents one.
Why does the answer come in gallons when I buy litres?: Because the data sheets are written by American manufacturers and quote square feet per US gallon. The calculator converts for you: a US gallon is 3.785411784 litres exactly, which is not the same as an imperial gallon at 4.546 litres. If a coverage figure you find elsewhere seems 20 percent generous, check which gallon it means. Every litre figure on this page comes from the US gallon.
Should I add extra for waste?: Buy up, do not calculate up. These are theoretical coverage rates, meaning they assume every drop that leaves the pail ends on the floor at the stated thickness. In practice some stays in the pail, some in the tray, some on the roller sleeve you throw away, and a two-part epoxy has a pot life measured in hours so you cannot mix a top-up later at leisure. Sherwin-Williams gives 30 minutes of sweat-in time and 4 hours of pot life at 25C on ArmorSeal 1000 HS. Round up to the next kit rather than adding a percentage you made up.
Can I use these rates for a different brand?: Only if that brand publishes its own volume solids and recommended film thickness, and you use those instead. Coverage is a property of a specific formulation: a 100 percent solids epoxy lays down roughly one and a half times the film of a 65 percent solids one from the same volume, because the difference is solvent that evaporates. Take the theoretical coverage from your own product's data sheet and this page's arithmetic still works. Take it from a different product and the number is fiction.

Sources

Both data sheets downloaded and read August 2026. Published technical data is subject to change by the manufacturer, so check the sheet in the box against the figures here before you buy.