How to measure
Measure each wall, then subtract doors and windows. Porous surfaces and strong color changes can need more paint.
How the estimate works
Net wall area × coats ÷ coverage per gallon. Add your allowance, then round up to whole cans.
A worked example
A 12 × 10 ft room with 8 ft walls has 352 sq ft of walls. Two coats at 350 sq ft per gallon, with 10% allowance, require 3 one-gallon cans.
Before you buy
Walls only; ceiling and primer are not included. Coverage varies by product and surface. Default values are illustrative starting points. Check the label and adjust them to your product.