Paint Calculator
Enter wall area, coats, coverage per litre and wastage to estimate the paint litres and bucket count needed.
Input Data
Results
At a glance:Paint needed = area × coats ÷ coverage per litre × (1 + wastage%). Bucket counts are rounded up to common can sizes (5 L, 18 L) so you buy whole cans.
Formula
Total area = area × coats.
Base litres = total area ÷ coverage.
With wastage (L) = base × (1 + wastage%); buckets = ceil(litres ÷ can size).
How to Use
- Enter the painting area (sum of all walls).
- Enter the number of coats.
- Enter coverage per litre and the wastage percentage.
- The tool returns required litres and 5 L / 18 L bucket counts.
Case Studies
100 m², 2 coats, 10 m²/L, 10% wastage
Total area = 100 × 2 = 200 m².
Base litres = 200 ÷ 10 = 20 L.
With wastage = 20 × 1.1 = 22 L; about 2× 5 L or 2× 18 L cans.
FAQ
Where do I find the coverage rate?
Coverage (spreading rate) is printed on the paint can, e.g. "10 m²/L". It varies with wall roughness, applicator and colour; rough or porous surfaces give a lower rate.
Why account for wastage?
Real painting loses paint at edges, joints, in tools and to touch-ups; budget an extra 5–15% typically. New or highly absorbent walls lose more, so 15–20% is reasonable.
Should primer count as a coat?
Yes. If you use a primer, include it in the coat count (e.g. 1 primer + 2 top = 3 coats). Different coats may have different coverage; this tool estimates with a single rate.
Is a big or small can better value?
Large cans (18 L) usually cost less per litre and suit large areas; small cans (5 L) are flexible with less leftover. Pick the combination closest to your total without waste.
Does a dark-over-dark colour need more paint?
Light over dark, or vivid colours, often need 1–2 extra coats for even coverage — raise the coat count accordingly. Repainting the same colour usually needs just one coat.
Why does the bucket count round up?
Paint is sold in whole cans, so even a fraction means buying one more; we use ceiling (ceil) to ensure enough. Seal leftovers for future touch-ups.
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References
Content review: Calculatorism Science Team. Results are for reference only; please refer to the relevant authorities for the official figures.