How the paint estimate works

Multiply the combined length of the walls by their height, then subtract the area of doors, windows, and other surfaces that will not be painted. Multiplying that net wall area by the number of coats gives total coverage demand. Dividing by the stated coverage on the paint container estimates gallons.

Measure the walls, not the floor

For a rectangular room, add the lengths of all four walls. Measure unusual alcoves or extra wall sections separately and include them in the total. Sloped ceilings, cabinets, trim, and accent walls should be measured according to the surfaces you actually plan to paint.

Coverage varies in real projects

Manufacturer coverage is a planning figure. Porous drywall, textured walls, strong color changes, application method, spills, and touch-ups can increase usage. Primer is a separate coating and may have a different coverage rate. Buying whole cans may leave reserve paint for later repairs, but container sizes and return policies vary.

This calculator estimates wall paint only in square feet and US gallons. Check the product label, surface preparation instructions, and measured room geometry before purchasing.