Interior paint
Enter a room size or wall area to get how many gallons of paint you need for any number of coats — with a money-saving gallon + quart buy split so you don't over-buy.
Paint needed
—Enter a room size to estimate paint.
| Paintable area | — |
|---|---|
| Paint (with coats) | — |
| Smart buy | — |
| Estimated cost | — |
Wall area is perimeter × height, minus the doors and windows you don't paint. Multiply by coats, divide by the coverage (about 350 sq ft per gallon), and round up — but we also show a gallon + quart split so a small overage doesn't cost you a whole extra gallon.
New drywall, patched spots, and big colour changes drink paint. Primer evens out the surface so your topcoat covers in the gallons estimated here — skip it and you may need an extra coat.
Coverage ≈ 350 sq ft/gal/coat; a quart ≈ a quarter of that. Estimates only.
Two coats is the norm for an even finish, and dark colours, bare walls, and covering an old colour almost always need it. The calculator defaults to two coats — drop to one only for a same-colour refresh over a sound surface.
New drywall and joint-compound patches drink paint unevenly. Prime them first so your topcoat covers in the gallons estimated here — skip it and you'll likely be back for another can.
Textured, brick, or porous walls can cover as little as 250–300 sq ft per gallon, and spraying wastes more than rolling. On a rough surface, lower the coverage figure so the estimate matches reality.
When you're just over a whole gallon, a gallon plus a quart is usually cheaper than two full gallons — and it keeps a little touch-up paint on hand. The smart-buy split shows when that's the cheaper option.
Find the wall area (perimeter × height), subtract doors and windows, multiply by the number of coats, and divide by the coverage (about 350 sq ft per gallon). A 12 × 14 ft room with 8 ft walls is 416 sq ft — about 2.4 gallons for two coats, so buy 2 gallons plus a quart.
Most interior wall paint covers about 350 sq ft per gallon per coat. Flat and primer can be a bit less; some premium paints claim 400. Bare drywall, patches, and dark-to-light changes soak up more — prime first.
Two coats is standard for an even finish and is what this calculator defaults to. One coat may do for a same-colour refresh over a sound surface; three for a drastic colour change over an unprimed wall.
If you need a little over a whole gallon, a gallon plus a quart is usually cheaper than two full gallons. The calculator shows that 'smart buy' split so you don't overpay or run short.
Prime bare drywall, patched spots, glossy surfaces, water stains, and big colour changes (especially dark to light) — otherwise the topcoat soaks in unevenly and you'll need an extra coat. A same-colour refresh over a sound wall usually doesn't need it. Primer isn't counted in the topcoat gallons.
The ceiling is length × width; divide by about 350 sq ft per gallon per coat. Ceilings almost always get two coats for an even look. Tick 'include the ceiling' and the calculator adds it to the gallons.
Usually one of three things: you estimated one coat but needed two, you skipped primer on a wall that drank the first coat, or the surface was textured or porous and covered less than 350 sq ft per gallon. When in doubt, buy the extra quart.
Estimate only, based on standard coverage. Actual coverage varies with paint type, surface, and colour change. Prime bare or patched walls and confirm coverage on the can before buying.