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Paint quantity calculator

Last updated . Editorial policy.

Measure the room, subtract the door and window areas you enter, multiply by coats, and divide by the coverage on your can. The result is gallons and quarts.

Coverage starts at 350 square feet per gallon, the low end of the 350 to 400 range Sherwin-Williams prints for SuperPaint Interior Latex Semi-Gloss A88 and PPG prints for Ultra-Hide Zero Interior. Change it. No price is shown unless you enter one.

Four-step paint quantity example for a 12 by 12 foot room with 8 foot walls: wall area 384 square feet, minus a door and two windows gives about 334, two coats make 668 square feet, and dividing by 350 square feet per gallon gives about 1.9, so buy 2 gallons.
Worked example of the paint quantity formula.

The 12 by 12 by 8 foot room is the worked example from the quantity guide. Door and window areas start at this site's editorial allowances (about 20 square feet per door, and 15 within the 10 to 15 window range). They are not measurements from a manufacturer. Coats start at 2 for that same example.

Result

48 ft of perimeter times 8 ft = 384 sq ft of wall, minus 20 sq ft of doors and 30 sq ft of windows = 334 sq ft. Times 2 coats = 668 sq ft.

Paintable area334 sq ft
Area times coats668 sq ft
At your coverage1.91 gallons (7.63 quarts)
Rounded up2 gallons

At 350 sq ft per gallon (low end of the cited range): 1.91 gallons, which rounds up to 2 gallons. At 400 sq ft per gallon (high end): 1.67 gallons, which rounds up to 1 gallon and 3 quarts.

No price entered.

What the numbers leave out

Texture, a porous wall, a big color change, and spraying all use more paint than the smooth-surface figure. The SuperPaint A88 application tips say that priming and two coats at the recommended film thickness can help where hiding a previous coating, or painting new drywall, is a factor. That sentence is not a rule for every product. Sherwin-Williams' paint calculator FAQ says a gallon of primer covers about 200 to 300 square feet. This page does not estimate primer, and it does not estimate trim.

The same FAQ says a quart covers 100 square feet, which matches the top of the 350 to 400 range divided by four. Quarts here are converted from the coverage you entered (one gallon is four quarts), then rounded up to the next whole quart.

If the room has to be wiped before guests arrive, dry to the touch is not the wash time. The cure-time guide uses the intervals on the product sheets and the 2026 dates USPS and Amazon Shipping publish. It does not set a sale or a shipping deadline. Color choice for those rooms is in the holiday hosting guide. A nearest screen color is the match finder.

Before you buy the gallons

Test the color first. The samples page covers peel-and-stick sheets and sample pots. The supplies below are tools for measuring and painting, not a price for the paint.

Test the color before the gallons

A quantity is only useful after the color survives a sample in your own light.

How to order a peel-and-stick sample →

Questions

How many square feet does a gallon cover?
Sherwin-Williams SuperPaint Interior Latex Semi-Gloss A88 lists 350 to 400 square feet per gallon at 4 mils wet and 1.5 mils dry. PPG Ultra-Hide Zero Interior lists 350 to 400 square feet per gallon on primed, smooth, nonporous surfaces. The coverage field starts at 350, the low end of that range. Replace it with the figure on your can.
How are doors and windows counted?
Only the opening areas you enter are subtracted. This page does not assume a door or window size. The quantity guide uses an editorial allowance of about 20 square feet per door and about 10 to 15 square feet per window. Those allowances are not manufacturer measurements. The example on this page uses 20 and 15 so it matches that guide.
Why does the result show quarts?
Paintable area times coats, divided by the coverage you entered, is the gallon figure. One US gallon is 4 quarts. The buy line rounds up to the next whole quart. That rounding is arithmetic, not a manufacturer instruction.
Does this calculator estimate a price?
No price is shown unless you type a price per gallon. This site does not publish paint prices. A cost, if you ask for one, is your number times the rounded-up quantity.
How long before holiday guests can I paint?
Dry to the touch is not ready to wash. The cure-time guide uses the dry, recoat and wash times on the product sheets and the 2026 dates USPS and Amazon Shipping publish. It does not add a sale or an order deadline. Use the sheet on your can.

Sources