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 | 350–400 sq ft/gal |
| New drywall (after primer or mist coat) | 300–350 sq ft/gal |
| Textured ceiling, rough render | 200–300 sq ft/gal |
| Brick, block, pebbledash | 150–250 sq ft/gal |
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 drywall: a coat of primer, then two finish 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 baseboards take a different product (trim enamel or semi-gloss) and are often missed. As a rough guide, one quart 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 can sizes.
This guide is general information for estimating. It is not engineering, legal or tax advice. Check local codes and your inspector for your project.