Paint Coverage Calculator

Paint Coverage Calculator works out paint for walls, ceilings, doors and cabinet panels from maker coverage ranges, then adds primer, extra for cutting in and the cheapest can mix.

Paint Coverage Calculator for Rooms and Cabinet Doors

Painters, remodelers and woodworkers finishing doors, shelves and paneling use the Paint Coverage Calculator to buy the right mix of quarts, gallons and pails. It takes wall or panel sizes, subtracts openings and applies the coverage printed on the maker's own data sheet.

Rooms are entered in feet and doors or cabinet panels in inches, measured at actual size rather than nominal size. The metric switch moves inputs and results to meters, centimeters and liters. Every calculation runs in square feet and gallons first and converts at the end.

Wall Area After Doors and Windows

The tool multiplies the room perimeter by the wall height, takes off every door and window, and then adds the ceiling or any extra area you enter.

$$A=2(L+W)\times H-(n_d\times a_d+n_w\times a_w)+A_c+A_x$$

L, W and H are the room length, width and height in feet. The n terms count doors and windows, and a is the area of one opening. The ceiling $A_c$ equals L times W when it is included, and $A_x$ is any extra area.

A 20 by 16 ft room with 8 ft walls has 576 sq ft of wall. One 36 by 80 in door (20 sq ft) and two 36 by 60 in windows (15 sq ft each) take off 50, which leaves 526 sq ft per coat. The tool removes the exact door size you pick, from 16.7 sq ft for a 30 in door to 40 sq ft for a 72 in patio door, instead of one flat figure for every door.

Room sides run to 500 ft and walls to 60 ft, with up to 100 doors and 200 windows. Coats run from 1 to 10 and the extra allowance from 0 to 100%. If the openings add up to more than the wall area, the tool shows an Openings Cover the Walls warning and holds the results. A garden shed works as a small room with the ceiling left off.

Door and Cabinet Panels, Faces and Edges

Switch What You're Painting to doors, cabinets or panels and the tool counts every face and every edge of every piece, not only the front you see when the door is closed.

$$A=N\times \frac{F\times L\times W+2(L+W)\times T}{144}$$

N is the piece count, F is one face or two, and L, W and T are length, width and thickness in inches. Dividing by 144 gives square feet. Enter the thickness you measure on the actual piece, since the presets only run from 1/2 in to 1-3/4 in.

Six 80 by 32 in doors at 1-3/8 in thick, painted on both faces and all four edges, come to 226 sq ft per coat. The faces alone are 213 sq ft, so the edges add 13 sq ft, or 6%. On a big kitchen those edges can decide whether two gallons is enough, as the cabinet question below shows.

Reading the Coverage Range on the Can

Paint makers print coverage as a range, and the range comes straight from film thickness. One US gallon holds 231 cubic inches, which spreads to 1,604 sq ft at a film 1 mil (0.001 in) thick, as coatings maker Dampney works out in its coating requirements guide.

$$C=\frac{1604\times VS}{DFT}=\frac{1604}{WFT}$$

C is coverage in square feet per gallon, VS is volume solids as a decimal, DFT is dry film in mils and WFT is wet film in mils. PPG's guide to its product data sheets gives the same rule, calls it the theoretical spreading rate and treats losses as a separate estimate.

The data sheets bear this out. Benjamin Moore prints 400 to 450 sq ft for Regal Select at 3.6 to 4.0 wet mils, and 1,604 divided by those two numbers gives 446 and 401. Behr's Multi-Surface Primer runs from 250 sq ft at 6.4 wet mils to 400 at 4.0. Sherwin-Williams' Emerald Interior is the exception, since its low end of 350 sits about 13% under the 401 that 4 wet mils gives.

That is why coverage falls from about 400 sq ft on an interior wall to 250 to 300 sq ft on an exterior paint. The exterior sheet simply asks for a thicker wet film.

Coverage Ranges in the Paint Coverage Calculator

Makers say the range depends on surface texture and porosity, so the tool lets you pick a smooth, average or textured surface. Smooth uses the top of the range, textured uses the bottom and average uses the midpoint. That split is the tool's own convention and not a maker figure.

$$C=C_{low}+(C_{high}-C_{low})\times s$$

Here s is 1 for a smooth surface, 0.5 for average and 0 for textured or bare. The paint volume then follows from the net area, the coats and an extra allowance.

$$V=\frac{A\times N}{C}\times (1+e)$$

V is gallons of paint, N is the coat count and e is the extra for cutting in and spills. The default of 10% is a trade convention. PaintPRO magazine puts the waste at 5% to 20% or more depending on brush, roller or spray, and Behr's data sheets say their coverage leaves out material lost to spraying.

A painter on an old ContractorTalk thread warned against trusting the label figure and called it optimistic in nearly every case. Raising the extra to 15% or 20% is the simple fix for sprayed jobs and dark colors.

The 526 sq ft room on Regal Select at its 425 sq ft midpoint needs 526 sq ft times 2 coats, divided by 425, plus 10%, which is 2.72 gallons. Three gallons cost $225 at the default prices. That beats two gallons plus three quarts at $240 and a $330 pail, so the tool suggests three gallons. It compares quarts, gallons and 5-gallon pails at your own prices.

Primer is figured on its own coverage and bought in whole gallons. Behr's Multi-Surface Primer prints 250 to 400 sq ft per gallon, and Benjamin Moore's Fresh Start High-Hiding All-Purpose Primer prints 400 to 450.

Coats and Primer by Maker

Sherwin-Williams' Emerald Interior sheet (11/2023) rates 350 to 400 sq ft at 4 mils wet and 1.6 dry. Its systems for drywall, plaster and wood call for two coats of Emerald, with a coat of primer under them on wood. For a drastic color change it says a coat of primer improves hiding.

Benjamin Moore's Regal Select sheet is self-priming on most properly prepared surfaces. It recommends two coats on bare substrates and allows one or two over previously painted surfaces. It also tells painters to estimate the whole amount up front, which keeps color uniform and cuts leftovers.

For doors and cabinets, the Advance sheet asks for new surfaces to be fully primed, with Fresh Start High-Hiding All-Purpose Primer listed for bare wood. Cabinetry should be sanded with 220 grit or coarser first, and lightly sanded between coats, which the sanding schedule calculator can plan. Advance recoats after 16 hours, and shelves or tabletops need five to seven days before going back into service, so the finish drying time calculator helps with the schedule.

Sherwin-Williams' Emerald Urethane Trim Enamel wants one coat of primer and two coats of enamel on drywall or wood, at 350 to 400 sq ft per gallon. Its sheet also says to patch holes with filler, sand smooth and prime every patched area, and the wood filler calculator sizes that step. The enamel is rated for exterior doors, trim and small areas, not the main body of a house.

Emerald Rain Refresh (3/2026) takes two coats on new bare surfaces and one coat on a repaint, at 250 to 300 sq ft per gallon. Behr's product guide lists Premium Plus interior at two coats and 250 to 400 sq ft, and its product page gives the same range. Its sheets add that certain colors need more than one coat for complete hide.

Litres, Cabinets and Label Claims

How much paint do I need for a 12 x 12 bedroom?

With 8 ft walls, one door and two windows, a 12 by 12 ft room has 384 sq ft of wall and 334 sq ft after openings. On two coats plus 10%, that is 1.73 gallons of Regal Select and 1.96 of Emerald Interior at their midpoints. Both fit two gallons.

Behr Premium Plus at its 325 midpoint needs 2.26 gallons, and Emerald at the low end of its range needs 2.10. The same room can need two or three gallons depending on the paint, which is why the tool asks for the product instead of a flat 350 or 400.

What area can 1 litre of paint cover?

One US gallon is 3.785 liters, so a gallon rating divided by 40.75 gives square meters per liter. Sherwin-Williams' Emerald Interior at 350 to 400 sq ft per gallon covers 8.6 to 9.8 m² per liter, the same metric range its trim enamel sheet prints. Regal Select covers 9.8 to 11.0 m², and Behr Premium Plus 6.1 to 9.8 m².

All of those figures are for one coat and before losses. Two coats halve them, so a liter of Regal Select paints about 4.9 to 5.5 m² of wall. Switch the tool to metric and it shows liters and square meters directly.

What area will 5 litres of paint cover?

Five liters cover 43 to 49 m² of Emerald Interior, 49 to 55 m² of Regal Select and 31 to 49 m² of Behr Premium Plus in one coat. A 2.5 L tin covers half of that, or 21 to 25, 25 to 28 and 15 to 25 m² in the same order.

On two coats, halve those figures again and allow for the extra. A 5 L tin of Regal Select then paints about 22 to 25 m² of wall once the 10% is counted, so measure the wall area in the tool before buying.

How many gallons of paint for kitchen cabinets?

A ContractorTalk member asked this about 35 doors at 30 by 22 in, 12 doors at 11 by 22 in and 9 drawer fronts at 15 by 6 in, painted on both sides with two coats. The poster guessed two gallons. The faces come to 372 sq ft on both sides, and 3/4 in edges add another 25 sq ft, for about 397 sq ft per coat and 795 sq ft over two coats.

At Benjamin Moore Advance's 400 to 500 sq ft per gallon and a 10% extra, that is 1.75 to 2.19 gallons. Two gallons works only at the generous end, and the poster also planned to paint the cabinet faces, so a third gallon or an extra quart is sensible.