Paint Calculator
Estimate topcoat, primer, putty and tools from your room size
Paint Quantity Calculator
Estimate wall and ceiling paint, primer, putty and tools from your room size. These are rule-of-thumb site figures, not manufacturer test data.
Room size & site conditions
Wall substrate
Results
| Item | Quantity | Basis |
|---|
How we calculate
- Coverage is taken as 10 ㎡ per litre per coat. Common interior emulsion covers 10–12 ㎡, so 10 is the conservative figure.
- Paintable area = walls + ceiling − doors and windows. The floor is not painted.
- Irregular walls, cornices, mouldings and dark or saturated colours use more paint; add 10–20% if any apply.
- Bucket counts are rounded up to whole packs of the size you selected.
- This is a quantity estimate only; always check the coverage printed on the bucket before buying.
How to treat the three substrates
| Substrate | Strip old finish? | Putty coats | Primer | Common problem |
|---|---|---|---|---|
| New plaster / skim coat | No, but repair hollow or cracked spots | 2 coats | One alkali-resistant primer | Thin putty shows through; corners crack easily |
| Repainting an old wall | Yes, remove flaking and powdery layers | 2–3 coats | One sealing primer | Old paint film has poor adhesion; painting over it peels |
| Bare cement render | No, but remove dust and loose sand | 3 coats including levelling | One alkali-resistant sealing primer | Efflorescence from cement makes the topcoat patchy |
Five common miscalculations
- Using the floor area as the paint area.
- Forgetting the ceiling.
- Not deducting doors and windows.
- Doubling the paint for each extra coat instead of multiplying area by coats.
- Pricing dark colours at the same coverage as light ones.