Paint Calculator

Gallons of wall paint for a room. Add up the wall lengths, enter the height, and the calculator takes off doors and windows.

–
gallons of paint
Wall area to paint–
Exact amount–
Primer (1 coat), if needed–

How it's calculated

Wall area is the total wall length times the height, less about 20 ft² per door and 15 ft² per window. Multiply by the number of coats and divide by the coverage on the can.

gallons = (length × height − doors × 20 − windows × 15) × coats ÷ coverage

Most interior wall paints cover 350–400 ft² per gallon on smooth, primed walls. Use 250–300 for textured walls, fresh drywall or a big color change. Two coats is standard.

Questions

How much paint for a 12×12 room?

With 8 ft walls, one door and two windows: about 334 ft², or just under 2 gallons for two coats.

Do I need primer?

Prime new drywall, patched areas, stained walls, and when switching from a dark color to a light one. Paint-and-primer products often cover a repainted wall in good shape without it.