MistriCalc → Paint Calculator
Paint Calculator
Litres of paint and the cost for any wall — enter the area or room dimensions, subtract doors and windows, then set coats and coverage.
Materials & quantities explainer
Run your numbers first, then read how it works. Start with the calculator below — the example values are pre-filled — then keep scrolling for the method, a worked example and the questions builders ask most. Everything runs in your browser; nothing you type is stored.
Calculator
To estimate paint, take the net wall area (walls minus doors and windows), multiply by the number of coats, and divide by the coverage per litre (about 110 sq ft per litre per coat). A typical 15 × 12 ft room, 10 ft high has about 540 sq ft of wall; minus 50 sq ft of openings and at two coats that is roughly 8.9 litres of emulsion.
Key takeaways
- Wall area = 2 × (L + W) × H.
- Litres = net area × coats ÷ coverage.
- Emulsion ≈ 110 sq ft/L per coat (smooth wall).
- Most repaints need 2 coats; new plaster a primer first.
- Round up to standard 1, 4, 10 or 20 L packs.
How paint quantity is calculated
The tool finds the wall area from the room perimeter and height, subtracts the openings you enter, multiplies by the coats, and divides by the coverage per litre.
If you already know the wall area, set length and width so 2 × (L + W) × H equals it, or simply read the litres from net area × coats ÷ coverage.
Worked example: a 15 × 12 ft bedroom, 10 ft high
Perimeter = 2 × (15 + 12) = 54 ft; gross wall = 54 × 10 = 540 sq ft. Subtract 50 sq ft of door and windows = 490 sq ft net. At 2 coats, painted area = 980 sq ft; at 110 sq ft/L, litres = 980 ÷ 110 = 8.9 litres. Round up to two 4 L tins plus a 1 L = 9 litres. At Rs 350 per litre, the cost is 9 × 350 = Rs 3,150.
Litres needed by wall area and coats (110 sq ft/L)
| Net wall area | 1 coat | 2 coats | 3 coats |
|---|---|---|---|
| 200 sq ft | 1.8 L | 3.6 L | 5.5 L |
| 400 sq ft | 3.6 L | 7.3 L | 10.9 L |
| 600 sq ft | 5.5 L | 10.9 L | 16.4 L |
| 800 sq ft | 7.3 L | 14.5 L | 21.8 L |
| 1,000 sq ft | 9.1 L | 18.2 L | 27.3 L |
Figures assume 110 sq ft per litre per coat; reduce coverage for rough or exterior surfaces.
Where this fits in your build
Paint is the last step after plaster and putty — size the plaster with the plaster calculator and the walls with the brick calculator. Tiling the dado or floor? Use the tile calculator.
Frequently asked questions
How much paint do I need per square foot?
About 1 litre per 110 sq ft per coat. A 400 sq ft wall at two coats needs ≈ 7.3 litres.
How do I calculate paint for a room?
Wall area = 2 × (L + W) × H, minus doors and windows, × coats ÷ coverage per litre.
How many coats do walls need?
Usually two over a primer; new plaster needs a primer/putty coat first, deep shades may need three.
What is the coverage of 1 litre?
About 110–140 sq ft per litre per coat on smooth walls; rough/porous surfaces cover less. Check the tin.
Should I subtract doors and windows?
Yes for accuracy — a door ≈ 21 sq ft, a window ≈ 12–15 sq ft. Skipping it just adds margin.
How is the cost worked out?
Buy litres (rounded up) × price per litre, in Rs. For the example, 9 L × Rs 350 = Rs 3,150. Round up to standard tin sizes.
Coverage of ≈ 110 sq ft (≈ 10 m²) per litre per coat reflects manufacturer datasheets for interior emulsion on smooth, primed surfaces; the first coat and rough/exterior surfaces cover less. Wall-area geometry (perimeter × height) is standard estimating practice. Always confirm coverage on the specific product tin.
Last reviewed 2026-06-14