How much paint do I need?
Enter the area you're painting and we'll work out the litres, tins and cost — and show you exactly how we got there, so you can check the maths and buy the right number of tins.
Tip: a wall is roughly length × height. A 4 m × 2.4 m wall ≈ 9.6 m².
| Emulsion paint | 1 × 5 L tin | £28 |
| Rollers, brushes, tape & dust sheets | 1 set | £25 |
- 1Area to paint: 30 m²
- 2Coats: 2 coats
- 3Coverage: 12 m² per litre, per coat (previously painted)
- 4Paint needed: 30 m² × 2 coats ÷ 12 = 5 litres
- 5Tins: 1 × 5 L tin
- Emulsion covers ~12 m²/L per coat on previously painted surfaces.
- Excludes a separate primer/undercoat to bare timber or stains.
How to work out paint quantity
- 1Measure the area
Wall area = length × height for each wall; add them up. A typical wall is 4 m × 2.4 m ≈ 9.6 m². Subtract big openings (a door ≈ 1.5 m², a window ≈ 1.4 m²).
- 2Decide the coats
Two coats is standard. Strong colour changes or bare plaster may need three (after a mist coat).
- 3Divide by coverage
Emulsion covers about 12 m² per litre per coat on previously painted walls, but only ~10 m²/L on new plaster, which is more absorbent.
- 4Round up to tins
Litres needed = area × coats ÷ coverage. Round up to whole 5 L or 2.5 L tins — it's worth having a little spare for touch-ups.
Most paint over- or under-buying comes from guessing the area or forgetting that bare plaster drinks paint. The formula is simple — area × coats ÷ coverage — and the calculator above does it for you and prints every step, so you're not taking a number on faith. That “show the working” approach runs through everything in ScopeWise: when we put a plastering or painting figure in your schedule of works, you can see exactly how many bags or litres it assumes.
Paint coverage quick reference
| Surface | Coverage per litre | Notes |
|---|---|---|
| Previously painted (smooth) | ~12 m² / coat | Standard matt emulsion |
| New / bare plaster | ~10 m² / coat | More absorbent — mist coat first |
| Textured / heavily prepped | ~8–10 m² / coat | Use the lower figure |
| 5 L tin (2 coats) | ~30 m² | Covers a small room's walls |
Indicative — always check the tin's stated coverage.
Frequently asked questions
How much paint do I need for one room?+
For an average double bedroom (walls ~30 m² after openings), two coats of emulsion needs roughly 5 litres — a single 5 L tin. Add the ceiling (~12 m²) and you'd want a little more. Use the calculator above for your exact dimensions.
How many square metres does a litre of paint cover?+
Around 12 m² per litre per coat on a smooth, previously painted surface, dropping to about 10 m²/L on new plaster and less on textured walls. Two coats roughly halves the area a litre covers.
Do I need a mist coat on new plaster?+
Yes. New plaster should get a 'mist coat' first — emulsion thinned with water (around 3:1) — to seal it, before your two top coats. The calculator's 'new plaster' option uses the higher paint requirement.
Should I buy extra?+
A little. Buying one consistent batch avoids slight colour variation, and you'll want some left for touch-ups. Rounding up to the next tin usually covers this.
Related tools & guides
Cost figures shown are indicative estimates, not quotations. You are responsible for verifying all costs (obtain contractor quotes) and any figures submitted to a lender. ScopeWise is a documentation tool, not financial, tax, structural or planning advice. HMO compliance prompts are guidance only — confirm requirements with your local council, as standards and licensing vary by authority.