Paint estimating is area × coats ÷ coverage. The skill is in choosing a realistic coverage figure for the surface in front of you.
Coverage rates in the real world
| Surface | Typical coverage |
|---|---|
| Smooth, previously painted wall | 12–14 m²/L |
| New plaster (after primer or mist coat) | 10–12 m²/L |
| Textured ceiling, rough render | 6–9 m²/L |
| Brick, block, pebbledash | 4–7 m²/L |
How many coats
- Same colour refresh: often one coat, but two gives a more even finish.
- Colour change: two coats, and three for strong colours or dark to light.
- New plaster or board: a diluted mist coat, then two full coats.
Deductions
Deduct doors and large windows. Don't bother with small openings: cutting in around them uses as much paint as the area you'd save.
Woodwork and trim
Doors, frames and skirting take a different product (trim enamel or satinwood or gloss) and are often missed. As a rough guide, one litre covers the trim of a typical bedroom with two coats.
Spraying
Airless spraying uses 20–30% more paint than rolling because of overspray, but it's much faster on large, empty areas.
The paint calculator splits wall and ceiling paint and picks sensible tin sizes.
This guide is general information for estimating. It is not engineering, legal or tax advice. Check the Building Regulations and Building Control for your project.