Paint calculator: gallons, quarts and coverage
Enter the wall size and the coverage off the can. This works out the gallons, and rounds that up to what you can actually buy.
Sum every wall for a whole room
0 if there are none
Advanced settings350 sq ft/gal · Roller
On the can, usually 350–400
Buy this much
1.96gallons
Buy
2 gal
Paintable area
312 sq ft
Overage
2%
Where the number comes from
- Gross wall area
- 352 sq ft
- Paintable areaAfter 40 sq ft of openings
- 312 sq ft
- Over 2 coats
- 624 sq ft
- Gallons before roundingIncludes 10% waste for roller
- 1.96
Where to buy this
- 2 galHome DepotLowe's
Have it all tinted in one order. A second batch of the same colour mixed later is close, not identical, and a wall shows it.
Plain search links, nothing sponsored. Prices and stock are the shop's, and a local lumberyard will usually beat both on solid stock.
Worked example: a room, two coats
44 ft of wall 8 ft high, less 40 sq ft of doors and windows, leaves 312 sq ft to paint — 624 sq ft over two coats.
At 350 sq ft a gallon, applied by roller, that is 1.96 gallons, so buy 2 gallons.
- Paintable area
- 312 sq ft
- Gallons needed
- 1.96
- Buy
- 2 gallons
These are the figures the calculator above opens on. Change any field and it works the same problem for your numbers.
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About paint coverage
- How much does a gallon of paint actually cover?
- Most interior wall paint covers 350 to 400 square feet per gallon on a smooth, primed surface — the number is printed on the can, and it is worth using your can's figure rather than a guess, since flat and eggshell cover more than a deep base tinted colour on the same wall.
- Why does spray use so much more paint than a roller?
- Overspray — paint that never lands on the wall at all, whether from a fine mist drifting past the edge or bouncing back off the surface. Spraying finishes fast and lays down an even coat, but plan on 20 to 30% more material than brush or roller for the same wall.
- Do I need to subtract windows and doors?
- For anything beyond a rough estimate, yes. A single door and a couple of windows can be 20 to 40 square feet you are not painting, and over a whole room that is most of the difference between buying exactly enough and buying a gallon you did not need.
- Should I round down to save a trip to the store?
- No — round up. Paint dries close enough in colour between cans of the same batch that this rarely matters, but running out mid-wall with a different can, or a different batch entirely, is the one mistake that actually shows on the finished wall.
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