How much paint do I need?

Common questions

How can I calculate how much paint I need?

Work out the paintable area, multiply by the number of coats, then divide by the coverage printed on the tin. The wall area is the room perimeter (twice the length plus twice the width) times the wall height; add the ceiling if you are painting it, and subtract the doors and windows. A 12 × 12 ft room with 8 ft walls, one door and one window comes to about 348 ft² of wall, so two coats at 350 ft² per gallon needs about 2 gallons. The calculator above does the whole sum for you in feet or metres.

How much will 1 gallon of paint cover?

About 350 to 400 square feet in one coat on a smooth, previously painted surface — roughly the walls of a small bedroom. Bare drywall, fresh plaster, render or a textured wall soaks up more and covers less, and a big colour change (light over dark, or the reverse) usually needs an extra coat. Use the spread rate on your tin as the real figure and type it into the coverage field; the calculator defaults to 350 ft² per gallon (about 11 m² per litre).

How much paint is for 1 sq ft?

At the common 350 ft² per gallon, one square foot needs about 1 ÷ 350 of a gallon per coat, which is roughly 0.0029 gallons or about 0.36 fluid ounces — so a single square foot is a tiny fraction of a tin. That is why paint is estimated by the whole wall, not the square foot: you total the area, multiply by coats, divide by coverage, and round up to whole gallons or litres because you cannot buy a part-tin.

How to calculate the amount of paint to use?

Use the formula paint = paintable area × coats ÷ coverage. Measure the room, add up the wall area (and ceiling if relevant), take off the openings, decide on the number of coats — two is the standard recommendation for an even finish and true colour — and divide by the coverage from the tin. Round the answer up to whole gallons or litres. The tool above applies exactly this and lets you adjust coats and coverage for your paint and surface.

How many gallons of paint for a 12x12 room?

A 12 × 12 ft room with 8 ft walls has 384 ft² of wall; leaving out one door and one window drops it to about 348 ft². Two coats at 350 ft² per gallon work out to roughly 2 gallons for the walls. Add the ceiling (another 144 ft², about one more gallon for two coats) if you are painting it, and round up — you can always keep the leftover for touch-ups.

Do you subtract doors and windows when calculating paint?

Yes — unlike wallpaper, large openings are worth deducting for paint because they genuinely get no paint and there is no offcut to save. The calculator subtracts a typical door (about 21 ft² / 1.95 m²) and window (about 15 ft² / 1.4 m²) for each one you enter. For an oversized patio door or picture window, increase the count or measure the opening and adjust, but you do not need to fuss over small windows — two coats and the round-up cover the slack.

Want the full walk-through? Read the paint guide →