Guide · Updated November 2026 · How we check our numbers

How Much Paint Do I Need for a Room?

Most paint cans cover about 350–400 square feet per gallon for one coat on smooth walls. Here is how to turn a room into gallons.

Step 1: wall area

Add up the lengths of all walls and multiply by the height. Walls totaling 48 ft in a room with 8 ft ceilings give 384 ft².

Step 2: subtract doors and windows

Subtract about 20 ft² per door and 15 ft² per window. With one door and two windows: 384 − 20 − 30 = 334 ft².

Step 3: coats and coverage

Two coats double the area to 668 ft². At 350 ft² per gallon, that is 1.91 gallons — buy 2.

When you need more

• Rough or textured walls absorb more paint.
• Big color changes may need primer or a third coat.
• New drywall should be primed first.

Ceilings and trim

Calculate the ceiling as length × width of the room, and buy trim paint separately — usually a quart is enough for doors and baseboards in one room.

Try the calculators

This guide is general information, not professional advice.