Understanding Paint Coverage and How Much You Need

A practical guide to estimating paint quantities, understanding coverage rates, and avoiding common painting mistakes.

Paint Coverage Rates

A gallon of standard interior latex paint typically covers 350 to 400 square feet (approximately 32 to 37 square meters) per coat on smooth, previously painted surfaces. Premium paints with higher pigment concentrations may cover slightly more, while thicker textured paints may cover less. The surface you are painting also matters: rough or porous surfaces like bare drywall, textured walls, or masonry absorb more paint and reduce coverage per gallon.

How to Calculate the Area You Need to Cover

Measuring wall area is straightforward geometry. Measure the width and height of each wall and multiply them together. Add up the areas of all walls you plan to paint. Then subtract the area of windows and doors.

Example: A 12 ft x 14 ft room with 8-ft ceilings: wall perimeter = 52 ft. Area = 52 x 8 = 416 sq ft. Subtract 2 windows (30 sq ft) and 1 door (21 sq ft) = 365 sq ft of paintable area. At 375 sq ft/gallon, that is ~1 gallon per coat, so buy 2 gallons for two coats.

Ceilings, Trim, and Easy-to-Forget Areas

When estimating paint needs, do not forget the ceiling and trim. Ceiling area is the room's length multiplied by width. For baseboards and trim, measure the total linear feet of all trim surfaces and multiply by the average width.

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