Find out exactly how much paint you need — enter room dimensions, coats, and coverage rate for an instant estimate.
Shorter wall of the room
Longer wall of the room
Floor to ceiling height (typical UK/EU: 2.4 m, US: 8 ft)
2 coats gives a solid finish in most rooms
Check the tin label — typically 10–14 m²/L
A paint calculator takes the guesswork out of buying paint. Instead of estimating by eye — and either running out mid-project or throwing away three half-used tins — you enter your room's exact measurements and get an accurate quantity in liters or gallons.
The calculator works by computing the total paintable surface area of your walls (and optionally the ceiling), subtracting the area taken up by windows and doors, multiplying by the number of coats, and dividing by your paint's coverage rate. The result tells you exactly how much product to buy before you even open the car door at the hardware store.
Getting this right matters more than most people realise. Buying too little means an emergency trip to the shop mid-job — and there's no guarantee the new tin will be the exact same batch colour. Buying too much wastes money and creates disposal problems, since most household paint cannot go in the bin or down the drain. A precise calculation solves both problems.
This tool supports both metric units (meters and liters, standard in Europe, Australia, and most of the world) and imperial units (feet and gallons, standard in the US). It handles any room shape, any number of coats, and lets you toggle ceiling coverage on or off.
The coverage rate is the key variable. Standard emulsion typically covers 10–14 m² per liter (350–450 sq ft per gallon) in a single coat. Exterior masonry paint covers less — around 6–9 m²/liter — because rough brickwork absorbs more product. High-build primers and specialist coatings often cover even less. Always check the tin and use the manufacturer's stated rate for the most accurate result.
The following table shows approximate paint quantities for 2 coats on walls only, at 12 m²/liter, with standard 2.4 m ceilings and one door (0.9 m × 2.0 m) and one window (1.2 m × 1.0 m):
| Room type | Typical dimensions | Net wall area | Paint (2 coats) |
|---|---|---|---|
| Small bedroom | 3.0 m × 3.5 m | ~27.5 m² | ~4.6 liters |
| Standard bedroom | 3.5 m × 4.5 m | ~33.4 m² | ~5.6 liters |
| Master bedroom | 4.0 m × 5.0 m | ~39.0 m² | ~6.5 liters |
| Small living room | 4.0 m × 5.0 m | ~37.8 m² | ~6.3 liters |
| Large living room | 5.0 m × 7.0 m | ~53.0 m² | ~8.8 liters |
| Kitchen | 3.0 m × 4.0 m | ~28.4 m² | ~4.7 liters |
| Bathroom | 2.0 m × 3.0 m | ~20.0 m² | ~3.3 liters |
| Hallway (straight) | 1.2 m × 5.0 m | ~23.5 m² | ~3.9 liters |
Values are approximate. Use the calculator above for your specific room dimensions.
Sarah is redecorating her 3.8 m × 4.2 m bedroom with 2.4 m ceilings. The room has one window (1.2 m × 1.0 m) and one door (0.9 m × 2.1 m). She'll apply 2 coats of mid-sheen emulsion at 12 m²/liter.
Wall area: (2 × 3.8 + 2 × 4.2) × 2.4 = 16.0 × 2.4 = 38.4 m². Subtract window: 1.2 m². Subtract door: 1.89 m². Net: 35.3 m². Total for 2 coats: 70.6 m². Paint: 70.6 ÷ 12 = 5.9 liters. Sarah buys two 3-liter tins (6 liters) — one tin left over for touch-ups.
Mark is painting his 18 ft × 24 ft open-plan living room with 9 ft ceilings. He has two large windows (5 ft × 4 ft each) and one door (3 ft × 8 ft). He plans 2 coats of flat paint at 400 sq ft/gallon.
Perimeter: (2 × 18 + 2 × 24) = 84 ft. Wall area: 84 × 9 = 756 sq ft. Windows: 2 × (5 × 4) = 40 sq ft. Door: 3 × 8 = 24 sq ft. Net: 692 sq ft. Total for 2 coats: 1,384 sq ft. Paint: 1,384 ÷ 400 = 3.46 gallons. He buys 4 gallons — keeping the remainder for touch-ups.
A newly plastered 4 m × 5 m bedroom with 2.5 m ceilings needs a diluted mist coat plus 2 full top coats. The mist coat uses a different coverage (about 5 m²/liter diluted). Using the calculator for the 2 top coats (12 m²/liter), net wall area ≈ 42 m², total for 2 coats = 84 m², paint needed = 7 liters. Add an extra ~4.2 liters at 5 m²/liter for the mist coat. Total: ~11 liters in three separate applications.
| Paint type | Typical coverage (m²/liter) | Typical coverage (sq ft/gallon) | Notes |
|---|---|---|---|
| Standard matt emulsion | 10–12 | 350–420 | Interior walls, most rooms |
| Premium matt emulsion | 12–16 | 420–550 | Better hide, fewer coats needed |
| Mid-sheen / eggshell | 12–14 | 420–480 | Kitchens, bathrooms, woodwork |
| Gloss paint | 14–17 | 480–580 | Skirting boards, doors, trim |
| Ceiling paint (flat white) | 10–13 | 350–440 | Usually thicker than wall paint |
| Exterior masonry paint | 6–9 | 210–310 | Rough surfaces absorb more |
| Primer / undercoat | 8–12 | 280–420 | Varies by surface porosity |
| Mist coat (diluted 3:1) | 4–6 | 140–210 | Fresh plaster only |
Calculate the perimeter of the room (2 × width + 2 × length), multiply by the wall height, subtract window and door areas, multiply by the number of coats, and divide by the coverage rate in m²/liter. Our calculator does all of this automatically. As a rough guide, a standard 4 m × 4 m bedroom needs about 6–7 liters for two coats.
Two coats is the standard recommendation for a solid, even finish. One coat is rarely sufficient to fully cover a previous colour. Three coats are needed for dramatic colour changes or to achieve a deep, saturated colour on light walls. Fresh plaster needs a diluted mist coat plus 2 top coats, totalling 3 applications.
Coverage (or spread rate) tells you how many square meters one liter covers in one coat. It is printed on the paint tin label — look for "theoretical coverage" or "spread rate." Standard emulsion covers 10–14 m²/liter. When in doubt, use 12 m²/liter as a conservative default.
You should subtract them for an accurate result. A standard door (0.9 m × 2.0 m = 1.8 m²) and window (1.2 m × 1.0 m = 1.2 m²) together represent about 3 m² — enough paint to cover a significant portion of a small bedroom. Including them leads to over-buying.
Yes. Ceiling paint is a different product — typically a flat, bright white designed to be applied overhead without drips. Calculate it separately using room width × room length. A 4 m × 5 m ceiling needs about 3.3 liters for two coats at 12 m²/liter.
Add 10% as a standard contingency. Keep the remainder in a sealed, labelled container — note the colour name, shade code, brand, and room. This makes future touch-ups seamless. Paint can change between production batches, so using leftover paint from the original job is always preferable to trying to match it later.
Split the room into rectangular sections and calculate each separately, then add the areas together. Alternatively, measure each wall individually (width × height), add all walls together, and subtract door and window areas. This works for any room shape.
Metric: square meters per liter (m²/L). Imperial: square feet per gallon (sq ft/gal). To convert: multiply m²/L by 40.7 to get sq ft/gal (approximately). So 12 m²/L ≈ 488 sq ft/gal. Our calculator handles both — just toggle the unit mode at the top.