Paint calculator

Find out how many gallons of paint you need for a room's walls, and the ceiling if you're painting it too.

Room length (feet)

Room width (feet)

Wall height (feet)

Doors

Windows

Coats123

Coverage (sq ft per gallon)

Include the ceiling

Calculate

How the calculation works

Wall area is the room's perimeter times the wall height. We subtract 20 sq ft for each door and 15 sq ft for each window, the standard allowances, then multiply by the number of coats and divide by the coverage of one gallon. 350 sq ft per gallon is a safe default for most interior paints; check your can and change it if needed.

Questions

How much paint do I need for a room?

Add up the wall area (perimeter × height), subtract about 20 sq ft for each door and 15 sq ft for each window, multiply by the number of coats, and divide by 350, the typical coverage of a gallon. A 10 x 10 ft room with 8 ft walls, one door and one window needs about 1.6 gallons for two coats.

How many square feet does a gallon of paint cover?

Most interior paints cover 350–400 sq ft per gallon on smooth, previously painted walls. Bare drywall, rough or textured surfaces can drop that to 250–300 sq ft, so check the label on your can.

Do I need two coats of paint?

Usually, yes. Two coats give an even colour and finish, especially when changing colour or painting over a dark shade. A paint-and-primer product over a similar colour can sometimes manage with one.

How much paint for a ceiling?

Multiply the room's length by its width. A 14 x 20 ft ceiling is 280 sq ft, about 0.8 gallons per coat. Tick the ceiling box to include it.

Should I buy quarts or gallons?

Buying a gallon is usually cheaper than four quarts. If you only need a little more than a whole gallon, a quart can top it up. We show both.

Why does my result differ from the paint store's?

Stores often add a margin for touch-ups and spillage. We give the exact figure for the area and coats you enter, so consider adding 10% for waste.