How much wall does one gallon of paint cover?

A gallon of interior wall paint typically covers about 350 to 400 square feet in a single coat, according to figures major manufacturers publish. This calculator uses 350 sq ft per gallon per coat as its default, and you can change that value to match the coverage rate printed on your specific can.

How many coats of paint do I need?

Two coats is the common recommendation for an even finish, especially over a new or differently colored surface. One coat may be enough when repainting a similar color over a good existing finish.

Does this include the ceiling?

No. This calculator estimates wall paint only. Ceilings, trim, and doors use different amounts and are often a different paint, so they are best calculated separately.

How is the cost estimated?

The cost is your estimated gallons multiplied by a price-per-gallon range you can edit. Paint prices vary a lot by brand, quality, and region, so the defaults are starting-point estimates — adjust them to the prices you actually see to get a figure you can trust.

Paint Calculator

Enter your room's dimensions to estimate how many gallons of paint you need and roughly what it will cost.

Room lengthftRoom widthftWall heightft

CoatsDoorsWindows

Paint quality

Adjust assumptions (coverage & price)

Coverage per coatsq ft/galPrice per gallon (low)$Price per gallon (high)$

Coverage defaults to 350 sq ft per gallon per coat — the low end of the 350–400 sq ft/gal range paint manufacturers commonly publish. The price range is a rough starting estimate, not a quote; paint prices vary widely by brand and region, so edit these to match the can and store you're buying from.

How the estimate works

We take the four walls of the room — two lengths and two widths, each multiplied by the wall height — to get the total wall area. Then we subtract a standard allowance for each door (about 21 sq ft) and window (about 15 sq ft), since you don't paint those. That paintable area is multiplied by your number of coats and divided by the coverage rate to get the gallons, which we round up to whole cans.

The two figures worth double-checking are the coverage rate and the price per gallon. Both are editable under “Adjust assumptions.” Coverage defaults to 350 sq ft per gallon per coat, the low end of the 350–400 sq ft/gal range manufacturers typically print on the can; using the low end gives a small buffer rather than leaving you short. Prices are rough starting estimates only — set them to what your store actually charges.

What you might need

Beyond the paint itself, most interior jobs also call for a paint roller kit, painter's tape, and a drop cloth. (Product links activate once our store account is approved.)

Frequently asked questions

How much wall does one gallon of paint cover?: A gallon of interior wall paint typically covers about 350 to 400 square feet in a single coat, according to figures major manufacturers publish. This calculator uses 350 sq ft per gallon per coat as its default, and you can change that value to match the coverage rate printed on your specific can.
How many coats of paint do I need?: Two coats is the common recommendation for an even finish, especially over a new or differently colored surface. One coat may be enough when repainting a similar color over a good existing finish.
Does this include the ceiling?: No. This calculator estimates wall paint only. Ceilings, trim, and doors use different amounts and are often a different paint, so they are best calculated separately.
How is the cost estimated?: The cost is your estimated gallons multiplied by a price-per-gallon range you can edit. Paint prices vary a lot by brand, quality, and region, so the defaults are starting-point estimates — adjust them to the prices you actually see to get a figure you can trust.