Paint Calculator

Total paintable area is wall area minus door and window cutouts, plus any ceiling area you're also painting. Multiply by the number of coats to get total square feet of paint. Divide by the can's coverage rating to get gallons. Rounding up to the nearest whole gallon gives the order quantity.

Most interior latex paints rate around 350 square feet per gallon on smooth, primed surfaces. Coverage drops on textured walls, raw drywall, and when going from dark to light. Coverage rises on smooth surfaces with a similar existing color. Use the number on your can; 350 is a reasonable starting estimate.

Two coats is the most common spec for a clean, even finish, especially on a color change. One coat works when you're refreshing a wall in the same color over a clean, primed surface. Three coats is occasionally needed for very saturated colors (deep red, bright yellow) or large color shifts.

The calculator uses 20 square feet per door (about a standard 3 ft × 6 ft 8 in door) and 15 square feet per window (a common large window). Smaller windows are usually offset by larger doors and trim, so the defaults are a fair planning estimate. Use a separate ceiling area input if you're also painting the ceiling.

Only if you're painting it. Leave the ceiling area field blank for walls-only jobs. Enter the ceiling's square footage (length × width of the room floor) to include it. Ceilings often need a flat or matte sheen paint, not the same can used for walls.

Yes, a little more. Touch-ups, drips, second-coat coverage on missed spots, and the inevitable color match for future repairs are all easier when you have leftover paint from the same batch. Buying one extra quart is usually plenty for a standard room.