Paint calculator guide
How much paint do I need for a bedroom?
A typical double bedroom — 12 × 14 ft — needs about 2 gallons of wall paint for two coats, and the same bedroom in the UK needs about 6.6 litres. Bedrooms are the room people repaint most, so the maths is worth doing once and doing right: measure the walls, subtract the door and windows, then divide by the coverage on the tin.
The quick answer
- US, 12×14 ft double bedroom, 2 coats: 365 sq ft of wall × 2 ÷ 350 = 2.09 gallons → buy 2 gallons + 1 quart
- UK, 3.6 × 4.3 m double bedroom, 2 coats: 33.2 m² of wall × 2 ÷ 10 = 6.6 litres → buy 5 L + 2.5 L
- Small bedroom (10×10 ft): 1.54 gallons → buy 2 gallons; in the UK about 4.8 litres → buy a 5 L tin
- Large master bedroom (16×20 ft): 3.0 gallons → buy 3 gallons; in the UK about 9.6 litres → buy a 10 L tin
- Add the ceiling and a 12×14 ft bedroom needs about 1 more gallon (UK: a 5 L tin) — see the ceiling section below
Run your own bedroom through the paint calculator — enter the room size, doors, windows and coats, and it works out the exact tins to buy, in gallons or litres.
The maths, step by step
Take a 12 × 14 ft bedroom with 8 ft walls, one door and two windows, painted in two coats. First the wall area: the perimeter is 2 × (12 + 14) = 52 ft, and 52 × 8 ft high = 416 sq ft of wall. Then subtract what you do not paint: a standard door is about 21 sq ft and each window about 15 sq ft, so 416 − 21 − 30 = 365 sq ft of paintable wall.
Two coats means covering 730 sq ft. Interior wall paint typically covers about 350 sq ft per gallon per coat on a smooth, primed wall, so 730 ÷ 350 = 2.09 gallons. You cannot buy 2.09 gallons, so the sensible buy is two 1-gallon cans plus a quart — 2.25 gallons — which leaves a little spare for touch-ups. Buying exactly 2 gallons would leave you a brush-stroke short on the last wall.
The same bedroom in metric: 3.6 × 4.3 m with 2.4 m walls. The perimeter is 15.8 m, so the walls are 37.9 m². Subtract one door (1.9 m²) and two windows (2.8 m²) to get 33.2 m². Two coats is 66.4 m², and at the usual UK figure of 10 m² per litre that is 6.6 litres — buy a 5 L tin plus a 2.5 L tin. As always, the figure on your own can beats any article's default — check it before you buy. The same step-by-step maths for a square room is in how much paint a 12×12 room takes.
How much paint for common bedroom sizes
Walls only, two coats, 8 ft / 2.4 m walls, one door and two windows deducted, at 350 sq ft per gallon (10 m² per litre). These are planning figures — bare plaster, textured walls and dark colour changes all need more, covered below.
| Bedroom | Wall area | Paint needed, 2 coats | Buy |
|---|---|---|---|
| 10 × 10 ft / 3 × 3 m | 269 sq ft / 24.1 m² | 1.54 gal / 4.8 L | 2 gal / 5 L |
| 12 × 12 ft / 3.6 × 3.6 m | 333 sq ft / 29.9 m² | 1.90 gal / 6.0 L | 2 gal / 5 + 2.5 L |
| 12 × 14 ft / 3.6 × 4.3 m | 365 sq ft / 33.2 m² | 2.09 gal / 6.6 L | 2 gal + 1 qt / 5 + 2.5 L |
| 14 × 16 ft / 4.3 × 4.9 m | 429 sq ft / 39.5 m² | 2.45 gal / 7.9 L | 3 gal / 10 L |
| 16 × 20 ft / 4.9 × 6.1 m | 525 sq ft / 48.1 m² | 3.00 gal / 9.6 L | 3 gal / 10 L |
A small box bedroom and a big master bedroom differ by roughly a gallon, so guessing from a single tin is how people end up mid-wall with an empty can. If your bedroom is not in the table, the paint calculator does the same maths with your exact room size.
Ceiling, trim and the feature wall
The ceiling is easy to forget and easy to add: a 12×14 ft bedroom ceiling is 168 sq ft, and two coats at the ceiling figure of 400 sq ft per gallon needs 336 ÷ 400 = 0.84 gallons — buy 1 gallon. In the UK the same ceiling is 15.5 m², needing about 3.1 litres for two coats — buy a 5 L tin. Full ceiling maths, including textured ceilings, is in how much paint a ceiling takes.
Trim — the door, skirting boards and window frames in a bedroom — takes roughly a quart in the US or half a litre in the UK of a separate trim paint, usually satin or semi-gloss so it can be wiped clean. Buy it separately; wall emulsion on trim scuffs fast and cannot be washed.
One feature wall is much cheaper than a whole room: a single 12 ft wall, 8 ft high, is 96 sq ft with nothing to subtract. Two coats is 192 ÷ 350 = 0.55 gallons — buy 1 gallon. In the UK the same wall is 3.6 × 2.4 m = 8.6 m², needing about 1.7 litres for two coats — buy a 2.5 L tin. A feature wall is also the cheapest way to test a bold colour before committing the whole bedroom to it.
Primer and colour changes
- New plaster or bare drywall: the first coat should be a mist coat — ordinary emulsion thinned with about 10–20% water — or a dedicated primer. Our 12×14 ft bedroom needs 365 ÷ 350 = 1.04 gallons for one mist coat, so buy 1 gallon plus a quart (UK: 33.2 ÷ 9 = 3.7 litres → a 5 L tin). Skipping it means the bare plaster drinks the topcoat unevenly and the finish patches.
- Previously painted, same colour: no primer needed. One coat can be enough for a refresh; two coats gives the proper finish.
- Dark to light: plan on two full coats, and a grey-tinted primer under white paint covers dark colours faster than white paint alone. A dark navy or deep green bedroom will drink a surprising amount of white — budget a full extra coat rather than a quart.
- Textured walls: add about 25% more paint — plan coverage at roughly 250–300 sq ft per gallon (about 7–8 m² per litre) instead of 350. Our 12×14 ft bedroom then needs 730 ÷ 300 = 2.43 gallons, so buy 3 gallons rather than 2 gallons plus a quart.
- Landlords repainting between tenants: bedrooms are usually the first rooms done in a void-period repaint, and the order — ceilings, then walls, then trim — is the same. The full void checklist is in repainting a rental between tenancies.
Frequently asked questions
How many litres of paint do I need for a bedroom?
A double bedroom (3.6 × 4.3 m) needs about 6.6 litres for two coats — buy a 5 L tin plus a 2.5 L tin. A small 3 × 3 m bedroom needs about 4.8 litres (buy 5 L), and a large 4.9 × 6.1 m master bedroom about 9.6 litres (buy 10 L). These figures use 10 m² per litre; textured walls need about 25% more.
How many gallons of paint do I need for a 12×12 bedroom?
About 1.9 gallons for two coats — buy 2 gallons. The walls are 333 sq ft after subtracting one door and two windows, two coats is 666 sq ft, and wall paint covers about 350 sq ft per gallon on a smooth, primed wall.
Is one coat enough for a bedroom?
For a same-colour refresh over a sound, previously painted wall with good paint, one coat can work — our 12×14 ft bedroom would then need only about 1.05 gallons (3.3 litres). For a colour change, over a mist coat, or where the old paint is patchy, two coats is the default. Bedrooms show roller marks under a lamp at night, and the second coat is what evens the finish out.
How much paint for just one bedroom wall?
One 12 ft wall, 8 ft high, needs about 0.55 gallons for two coats — buy 1 gallon. In the UK the same wall (3.6 × 2.4 m) needs about 1.7 litres — buy a 2.5 L tin. That is the usual amount for a feature wall.
Coverage figures are planning estimates — interior wall paint typically lists about 350 sq ft per gallon (10 m² per litre), and textured walls take about 25% more. Always confirm coverage on the can. Read how the calculator's default assumptions were chosen on the About page.