Paint calculator
Room size in, litres or gallons and tins out.
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Example
Example: a 14 × 12 ft bedroom in a new colour — 2 gallons and a quart
A bedroom 14 ft by 12 ft with 8 ft walls, one door and two windows, painted a new colour: 2 coats. Coverage left empty, so 350 sq ft a gallon is used.
- Walls: 2 × (14 + 12) × 8 = 416 ft², less 21 ft² for the door and 2 × 15 ft² for the windows: 365 ft².
- Two coats: 730 ft² ÷ 350 ft² a gallon = 2.09 gal.
- Rounded up to the cans sold (5 gal, 1 gal and 1 qt): 2 × 1 gal + 1 × 1 qt = 2.25 gal.
| What | Area | Paint | To buy |
|---|---|---|---|
| Walls, 2 coats | 365 ft² | 2.09 gal | 2 × 1 gal + 1 × 1 qt |
| Walls and ceiling, 2 coats | 533 ft² | 3.05 gal | 3 × 1 gal + 1 × 1 qt |
| Walls, 1 coat (same colour) | 365 ft² | 1.04 gal | 1 × 1 gal + 1 × 1 qt |
| Walls, 2 coats, can says 400 ft²/gal | 365 ft² | 1.83 gal | 2 × 1 gal |
2.09 gallons: two gallon cans and a quart. Ticking the ceiling adds 14 × 12 = 168 ft² and makes it 3.05 gallons. If your can says 400 sq ft a gallon, type that in and two gallons do.
How it works
- Type the room’s length, width and wall height, and how many doors and windows it has.
- Choose the number of coats — two for a new colour — and type the coverage printed on the tin if you know it.
- You get the wall area, the paint needed and the tins to buy; tick the ceiling to add it.
Frequently asked questions
- How much paint do I need for a room?
- Wall area = 2 × (length + width) × height, minus about 21 sq ft (2 m²) a door and 15 sq ft (1.5 m²) a window. Multiply by the coats and divide by the coverage: a 12 × 10 ft room with 8 ft walls, one door and one window is 316 sq ft; two coats at 350 sq ft a gallon need 1.8 gallons.
- What coverage should I use?
- The one on the tin: typically 350–400 sq ft a gallon, or 8–12 m² a litre. Rough plaster, bare drywall and dark-to-light changes use more; a primer helps.
- How many coats do I need?
- Two coats for a new colour or a fresh wall; one may do when repainting in the same colour.
- Is the result exact?
- It is an estimate from standard figures. Walls are rarely perfectly square and surfaces absorb differently, so buy a little extra from the same batch, and check the figures on the product you choose.
- How much paint do I need for a ceiling?
- Tick Paint the ceiling too: its area, length × width, is added before the coats are counted. For a 14 × 12 ft room that is 168 ft², so walls and ceiling at two coats come to 3.05 gallons instead of 2.09.
- Can I work in litres and square metres?
- Yes: set Units to Metric. A door then counts as 2 m², a window as 1.5 m², the coverage is 10 m² a litre unless you type the one on the tin, and the tins are 10, 5, 2.5 and 1 litre.
- Is anything uploaded?
- No. It is worked out in your browser, and nothing you type leaves your computer.
Made for a specific use
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