🎨 Paint Calculator
Enter your rooms or walls: get the area to paint, the litres you need and the cans to buy with as little left over as possible.
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About the Paint Calculator
How many litres of paint do you need to redecorate a bedroom or a living room? This calculator measures the real area to paint (walls, ceilings, openings deducted), applies the number of coats and your paint’s coverage, then suggests the combination of cans that leaves the least paint over.
How to Use the Calculator
- Add your rooms (length × width × ceiling height) or single walls (length × height).
- Tick ceilings if you are painting them too.
- Enter the doors and windows to deduct, with their sizes.
- Pick the paint, the surface and the number of coats, then the can sizes on sale (and their prices if you want the cost).
Formulas Used
- Room walls: perimeter × height = 2 × (length + width) × height. Ceiling: length × width.
- Area to paint: walls − doors − windows + ceilings.
- Litres: area × number of coats × surface factor ÷ coverage (m²/L), plus the waste margin (10% by default).
- Suggested coverage: matt acrylic 9 m²/L, satin 11, primer 8, exterior 6, enamel 12: average values; the figure on your can prevails.
- Cans: if you enter a price for every can size, the tool picks the cheapest combination that covers the need (then the fewest cans). Otherwise it balances leftover paint and number of cans: each extra can counts as 0.25 L of leftover, so 6.9 L becomes 3 × 2.5 L rather than 6 small cans.
Tips
- Primer: on new plaster, bare wood or a strong colour change, apply a primer first; work it out separately with its own coverage.
- Same batch: buy all the tinted paint at once, machine-tinted colours vary between batches.
- Keep a little paint for touch-ups.
- Dark colour over light (or the reverse): a third coat is often needed.
Common Mistakes and Limits
- Using the maximum coverage on the can: it is measured on a smooth, non-absorbent surface.
- Forgetting a coat: most wall paints need two coats.
- Non-rectangular surfaces (sloping ceilings, gables): enter them as single walls with an average height.
- Estimate only: the application method (roller, sprayer) and the surface change the actual consumption.
Privacy & Security
- 100% in your browser: no data is sent to a server.
- No sign-up: free and instant.
- Works offline once the page has loaded.