Interior paint coverage

Rectangular room, walls only. Subtract typical door and window rectangles, then divide by coverage. Not a contractor quote.

Enter feet.

Length (ft)

Width (ft)

Height (ft)

Doors Typical opening, not manufacturer coverage.

Windows Typical opening, not manufacturer coverage.

Coats

How far one gallon goes (sq ft) How much wall one gallon covers. Leave this at 350 unless your paint can says a different number. 350 is Sherwin-Williams’ official low estimate, so we tell you to buy enough.

Sources

Coverage figures on this page come only from these official links. Last opened 2026-08-24. Door and window sizes are typical openings, not manufacturer coverage.

Product	What we use	Official page
Sherwin-Williams SuperPaint PDS	350–400 sq ft/gal at 4 mils wet	sherwin-williams.com SuperPaint PDS
Sherwin-Williams FAQ	Use the product data page for coverage	sherwin-williams.com paint FAQ

Assumptions

Wall area = 2 × (length + width) × height. Ceiling and floor are not included.
Default coverage is 350 sq ft/gal. Edit the field to match the can. Official range is on the sources table.
Each door subtracts 20 sq ft (3 ft × 6 ft 8 in typical interior door opening). This is a typical opening, not manufacturer coverage.
Each window subtracts 15 sq ft (3 ft × 5 ft typical opening). This is a typical opening, not manufacturer coverage.
Openings that exceed wall area are clamped to zero remaining paint area.
Purchase gallons are rounded up. The raw (unrounded) number is also shown.

Trim, texture, waste, primer, and odd walls will move the number. This is an estimate, not a contractor quote.