Paint Calculator

How it works

Most interior paints cover about 350 ft² per gallon for one coat. This calculator multiplies your wall area by the number of coats and divides by 350 to estimate gallons needed. For accurate results, measure the total perimeter of the room (sum of all wall lengths along the floor) and the wall height; multiply for gross wall area, then subtract about 21 ft² per door and 15 ft² per window to get paintable area.

Two coats is standard for new paint or color changes. Some bold colors (deep reds, vibrant blues) need three coats. A primer-and-paint-in-one product can save a coat over bare drywall but rarely saves anything when going from light to dark or covering stains.

Coverage varies. Smooth walls (drywall, plaster) are at the high end of the 350 ft² range. Textured walls (popcorn ceiling, stucco, knockdown) absorb more paint — drop coverage to 250-300 ft² per gallon and add 15-20% to your estimate. Brick, masonry, and rough wood are at the bottom — ~200 ft² per gallon.

Buy a little extra. A leftover quart for touch-ups is invaluable later (bumps, scuffs, repairs). Paint stays usable for 2-5 years if sealed properly. Worse, running out mid-project means a second store trip and possible color-batch mismatch — even the same paint code can vary 1-3% between mixings, visible on adjoining walls.

Cost factors. Quality matters more than coverage when it comes to paint. Premium paints ($60-90/gal) cover better, hide stains in fewer coats, level smoother, and last longer than budget paints ($25-35/gal). The labor cost (your time or a painter's hourly rate) usually dwarfs the paint cost — saving $30 on a gallon of cheaper paint isn't worth the extra coat or worse finish it produces.