worldofcalcsPaint Calculator
Area to paint
515 sq ft
Paint needed
10.3 L
Packs to buy
1 × 10 L + 1 × 1 L
Walls 440 − doors and windows 45 + ceiling 120 sq ft
Coverage varies by paint and wall. Check the spreading rate on the label: if it is given for 2 coats, enter double that figure here.
How much paint does a room need?
Add up the area of the four walls, take off the doors and windows, and add the ceiling if you're painting it. Multiply by the number of coats and divide by how many square feet a litre covers. This calculator does that in square feet and suggests the packs to buy from the usual 1, 4, 10 and 20 litre sizes.
Paint formula
Wall area = 2 × (length + width) × height · Area = walls − doors − windows + ceiling · Litres = area × coats ÷ coverage per litre
A door is taken as 3 × 7 ft (21 sq ft) and a window as 4 × 3 ft (12 sq ft). The ceiling is length × width.
Painting tips
- New plaster usually needs putty and a coat of primer before the paint. Old painted walls in good condition often need only the top coats.
- Two coats give an even colour. A big colour change, such as dark to light, may need a third.
- Spreading rates differ between distemper, emulsion and enamel, and rough or porous walls drink more paint. Use the figure on the label.
- Buy all the paint for a room from the same batch if you can, as shades can vary slightly between batches.
- Keep a little paint for touch-ups later.
Worked example: a 12 × 10 ft room
- Room 12 × 10 ft with 10 ft walls, 1 door and 2 windows, ceiling included
- Walls: 2 × (12 + 10) × 10 = 440 sq ft
- Less 1 door (21) and 2 windows (24): 395 sq ft; plus the ceiling (120): 515 sq ft
- 2 coats at 100 sq ft per litre: 515 × 2 ÷ 100 = 10.3 litres
- Buy a 10 litre and a 1 litre pack
Paint for common room sizes
Walls 10 ft high, ceiling included, 2 coats at 100 sq ft per litre per coat.
| Room | Doors / windows | Area (sq ft) | Paint (litres) |
|---|---|---|---|
| 10 × 10 ft | 1 / 1 | 467 | 9.3 |
| 12 × 10 ft | 1 / 2 | 515 | 10.3 |
| 12 × 12 ft | 1 / 2 | 579 | 11.6 |
| 14 × 12 ft | 1 / 2 | 643 | 12.9 |
| 16 × 12 ft | 2 / 2 | 686 | 13.7 |
| 20 × 15 ft | 2 / 3 | 922 | 18.4 |
Deducts 21 sq ft per door and 12 sq ft per window.