Field guide
Concrete Coating Coverage Calculator: How Much Material Your Floor Needs
Use the calculator on this page to estimate how much coating and flake your floor needs, then read the rest of the page to understand why any single coverage number is only a starting point. Coverage on a real slab is governed by porosity, surface profile, film thickness and what job the coat is doing, and those four variables move the answer by a wide margin.
Use the calculator on this page to estimate how much coating and flake your floor needs, then read the rest of the page to understand why any single coverage number is only a starting point. Coverage on a real slab is governed by porosity, surface profile, film thickness and what job the coat is doing, and those four variables move the answer by a wide margin.
The reason most coverage advice is wrong is that it quotes one number per product. A gallon of 100 percent solids epoxy might cover close to 200 square feet as a thin solid color coat on a smooth, tight slab, and barely 120 square feet as a flake broadcast base coat on an open, ground slab. Same gallon, same product, nearly a two to one difference, driven entirely by what you are asking the coating to do.
Below the calculator you will find the coverage math itself, how solids content and mil thickness fit together, what porosity and CSP profile do to consumption, how base coats, broadcast coats and topcoats differ, how to size flake by weight, and what waste factor to carry. If you want a second set of eyes on a material list before you order, call 817-676-6793 with your square footage and system.
How much material do I need?
Enter the slab. We will give you a range, because porosity and surface profile change real coverage.
- Floor area
- 400 sq ft
- Base coat
- 3.1 to 3.4 gal
- Topcoat (1 pass)
- 3.1 to 3.4 gal
- Flake
- about 8 x 25 lb boxes
Base coat, flake broadcast to rejection, then a clear topcoat. Order roughly 10% over on a first job.
The coverage math, and why it works
There is one piece of arithmetic underneath every coverage figure in the industry. A gallon of liquid spread one mil thick covers 1,604 square feet. That number is fixed, it comes from unit conversion, and it anchors everything else.
Two things reduce it. First, solids content: only the solids stay on the floor, so a coating that is 50 percent solids by volume delivers half the dry film. Second, the film thickness you are targeting. So theoretical coverage in square feet per gallon equals 1,604 multiplied by the solids fraction, divided by the target dry film thickness in mils. A 100 percent solids product at 10 mils gives roughly 160 square feet per gallon in theory, and roughly 267 at 6 mils.
That is theory, and theory assumes a flat, non-absorbent surface with zero waste, which describes no concrete floor anywhere.
- One gallon at 1 mil thick covers 1,604 square feet. This is a conversion, not a product claim.
- Theoretical square feet per gallon = 1,604 x solids fraction / target mils.
- 100 percent solids at 10 mils is roughly 160 sq ft per gallon in theory.
- Theoretical coverage assumes a flat, non-porous surface and no waste. Concrete is neither.
Why a single coverage number is misleading
Manufacturers publish a coverage range because coverage is a range. When you see 175 to 250 square feet per gallon on a data sheet, that is not hedging, it is an honest statement that the same product behaves differently depending on where it goes.
A smooth, previously sealed, lightly abraded slab sits at the top of the range. A freshly ground, open, absorbent slab sits at the bottom, and a badly worn or porous slab can fall below it. The concrete pulls material into the pore structure before any film starts to build on the surface, and none of that material contributes to your dry film thickness.
The practical consequence is that estimating from the high end of a published range is how crews run out of material at four in the afternoon with a wet edge going. Estimate from the low end, and treat the high end as upside.
- Published coverage ranges reflect real substrate variation, not vagueness.
- Estimate from the low end of the range, not the middle and definitely not the high end.
- A previously coated or sealed slab that has been abraded consumes far less than a freshly ground bare slab.
- Running out mid-floor costs more than a spare pail does.
Porosity and surface profile
Two slabs of identical square footage can consume materially different amounts of the same coating, and the two drivers are porosity and profile.
Porosity is about how thirsty the concrete is. Hard troweled, dense, low water to cement ratio concrete absorbs relatively little. Older, weathered, soft or heavily worn concrete absorbs a great deal. So does anything that has been aggressively ground down past the dense surface layer. You can test this on site with the same water drop check used to look for sealers: water that disappears quickly indicates concrete that will drink coating just as fast.
Profile is about surface area. A ground concrete surface profile is not flat, it is a field of peaks and valleys, and a deeper profile means more actual surface to cover and more valley volume to fill before the peaks are covered at your target thickness. That is why a coating over a deeper profile consumes more per square foot, and why applying a thin film coating over an aggressive profile both wastes material and risks burning through on the high points.
Priming changes both. A primer coat seals the pore structure, so the finish coat that follows lands on a surface much closer to the theoretical assumption. On very porous concrete, priming often costs less in total material than letting the base coat do the priming for you.
Base coat, broadcast coat, topcoat: three different rates
The single biggest reason estimates go wrong is applying one coverage number to every coat in the system. Each coat has a different job and a different consumption rate.
A base coat under a flake broadcast has to carry enough wet film to accept and hold the chip, so it goes down heavier than the same product would as a solid color coat. Flake pulling loose under the scraper is almost always a starved base coat. A solid color coat just needs to build film and hide the substrate, so it runs at the lighter end of the product's range, though strong color changes may need a second coat for hide regardless of mils.
A topcoat over a full broadcast flake floor consumes far more than a topcoat over a smooth floor, because the flake surface has substantially more surface area and texture to fill. The first topcoat over broadcast flake is largely absorbed by that texture. This is the most common material shortfall on a flake floor.
- Flake base coat: heaviest rate in the system. Never stretch it.
- Solid color coat: lighter rate, but check hide as well as mils on strong color changes.
- First topcoat over full broadcast flake: much heavier than over a smooth floor.
- Second topcoat: closer to the product's normal rate because the profile is already filled.
- Primer: often the lightest rate, and often the coat that saves you material overall.
Mil thickness, wet film and dry film
Mils are thousandths of an inch, and coatings are specified in two of them. Wet film thickness is what you have on the floor while it is still liquid. Dry film thickness is what remains after cure. On a 100 percent solids product they are close to identical, because nothing evaporates. On a 50 percent solids product, 10 mils wet becomes roughly 5 mils dry.
The reason this matters on the floor is that wet film thickness is the only one you can control in real time. A wet film gauge is an inexpensive metal comb, it takes a few seconds to use, and it is the only way to know whether the coat going down matches the coat you estimated. Check it early in the first section, adjust the roll rate, and check again.
The other way to verify rate is arithmetic: divide the area you covered by the gallons you used and compare against the plan. If a crew has pulled three gallons across 600 square feet on a coat that was supposed to run at 160 square feet per gallon, they are 25 percent light and you can fix it before the whole floor is wrong.
Sizing flake by the box
Flake is estimated by weight per square foot, not by gallons, and the number depends entirely on broadcast style. A full broadcast to rejection saturates the floor and uses several times the flake of a partial broadcast where chip is scattered as an accent over a visible base color.
Because you throw more chip than sticks, a full broadcast job has two numbers: how much flake you have to have on site, and how much actually stays on the floor. The difference is reclaimed after the scrape, and screened reclaimed flake is fine to reuse on the same floor.
Two ordering rules save trouble. First, order all the flake for one floor from a single lot where possible, because blend color can vary between production runs and the line where two lots meet stays visible. Second, order a full box over the estimate rather than a partial. Running short mid-broadcast means either a visible thin band or recoating and rebroadcasting the whole section.
- Estimate flake by pounds per square foot for your broadcast style, then convert to boxes.
- Full broadcast to rejection uses several times what a partial broadcast uses.
- Plan to reclaim, screen and reuse the excess on the same floor.
- Order one lot per floor, and round up to the next full box.
Waste factor and what to keep on the truck
Every estimate needs a waste factor on top of the calculated quantity. Material stays in the pail, in the roller cover and on the mixing paddle, kicks in the bucket when a phone call runs long, and gets spent on cut-in and edging, which always consumes more per square foot than the open field does.
A waste allowance of 10 to 15 percent is a common planning figure for a straightforward open floor. Push it higher on floors with heavy cut-in, many columns or complicated geometry, and higher again on fast chemistry where a mistimed batch cannot be recovered.
Beyond the waste factor, carry a contingency kit. A spare base coat kit and a spare topcoat kit on the truck cost nothing if unused and save a return trip when a slab turns out thirstier than it looked. On a fast cure system that return trip is worse than the material, because coming back after the recoat window has closed means abrading the floor first.
Common floor sizes and how to measure
Measure the floor rather than trusting the label on the space. A two car garage is commonly quoted at anywhere from 400 to 600 square feet, which is a wide enough band that using the phrase instead of a tape measure will cost you a pail.
Measure length by width for the main rectangle, then add or subtract alcoves, bump-outs and equipment pads. Deduct fixed obstructions only if they are large. A water heater platform is worth deducting, a support column is not. Do not forget vertical surfaces if they are in scope. Coved base, curbs, equipment pads and the first few inches up the wall all take material, and they consume at a higher rate per square foot than the flat field because of how they are cut in.
If you would rather have a person check the arithmetic, call 817-676-6793 with your dimensions, your system and your broadcast style and Twin Coating Supplies will build the material list with you.
Frequently asked
How much epoxy do I need for a 2 car garage?
A two car garage is typically 400 to 600 square feet, so measure the floor before ordering rather than relying on the description, because that range is wide enough to cost you a pail of base coat. At a flake base coat rate near 120 to 130 square feet per gallon, a 500 square foot garage needs roughly 4 gallons of base coat plus topcoat, flake and a waste allowance.
How do you calculate epoxy coverage?
Epoxy coverage is calculated from the fact that one gallon spread one mil thick covers 1,604 square feet, so theoretical coverage equals 1,604 multiplied by the product's solids fraction and divided by your target dry film thickness in mils. Then reduce that figure for concrete porosity, surface profile and a waste allowance.
Why does the same epoxy cover different amounts on different floors?
The same epoxy covers different amounts on different floors because concrete porosity and surface profile change how much material the slab absorbs before any film starts to build, and none of the material that soaks into the pore structure contributes to your dry film thickness. A dense, previously sealed slab sits at the top of the published range. A freshly ground slab sits at the bottom.
What is a good waste factor for a coating estimate?
A waste allowance of 10 to 15 percent over the calculated quantity is a common planning figure for a straightforward open floor, covering what stays in the pail, in the roller cover and on the mixing paddle, plus cut-in and edging. Increase it for columns, complicated geometry and fast cure chemistry, and carry a spare kit on the truck.
How many mils thick should an epoxy floor be?
Target film thickness is set by the coating manufacturer for each product and system, and it varies from a few mils for thin film topcoats to considerably more for heavy build epoxy systems. Check wet film thickness on the floor with a wet film gauge as you apply, since that is the only measurement you can correct in real time.
How much flake do I need per square foot?
Flake is estimated by weight per square foot and depends entirely on broadcast style, with a full broadcast to rejection using several times the chip of a partial accent broadcast. Order all the flake for one floor from a single lot to avoid visible color variation, and round up to the next full box.
Does the first topcoat over flake use more material?
The first clear topcoat over a full broadcast flake floor consumes noticeably more material than a topcoat over a smooth slab, because the flake surface has far more surface area and texture to fill. That first coat mostly fills and seals the profile, and the second coat produces the finished gloss and wear surface.
What is the difference between wet film and dry film thickness?
Wet film thickness is the coating depth on the floor while it is still liquid, and dry film thickness is what remains after the coating cures, so the gap between them is set entirely by the product's solids content. On a 100 percent solids product the two are nearly identical. On a 50 percent solids product, 10 mils wet cures down to roughly 5 mils dry.
Should I prime porous concrete before coating it?
Priming porous concrete is usually worth it, because a primer seals the pore structure so the finish coat builds film on the surface instead of disappearing into the slab, which is where a large share of estimating error comes from. On very absorbent concrete a primer coat often reduces total material use, and it also reduces outgassing bubbles under fast curing coatings.