Measure the room
For a rectangular room, record its length and width in feet. The perimeter is twice the sum of those measurements.
Measure wall height
Record wall height in feet. The calculator assumes four walls of the same height. Treat sloped ceilings or irregular walls as separate calculations.
Subtract openings
Measure the height and width of each door or window. Multiply those dimensions for each opening and add their areas together. Enter that combined square-foot amount.
Choose coats and coverage
Enter your planned coat count and the coverage per gallon stated for your paint. Read the product’s preparation and coverage information. The result rounds up to whole gallons.
A 12 × 15 ft room with 8 ft walls has 432 sq ft of wall area. Subtract 40 sq ft of openings: 392 sq ft. Two coats cover 784 sq ft in total.
Keep in mind
The calculator covers walls only. Ceilings, trim, primer and preparation are separate. Product coverage can vary with the surface and application.
Planning guidance only. Confirm measurements and product requirements before buying. Read the calculator disclaimer.