How much paint do I need? How to use the paint calculator
- 1Choose what you are painting: a whole room, one wall, or an area you already know.
- 2Enter the sizes. Doors and windows start at 1 each — change the number and sizes to match your room.
- 3Pick the type of paint and the number of coats; the coverage fills in by itself.
- 4Pick your tin size, and tick primer or putty if the walls are new or bare.
How to calculate paint for a room (formula)
- 01Wall area = 2 × (length + width) × height − doors − windows − areas not painted
- 02Paint = area × coats ÷ coverage
- 03Tins = paint ÷ tin size, rounded up (walls and ceiling counted separately)
- 04Primer = area ÷ primer coverage (1 coat); putty = area × about 0.6 kg/m²
Paint makers quote coverage for one coat on a smooth, previously painted wall — often 10–16 m² per litre for emulsion, or 350–400 ft² per US gallon. We start at 10 m²/L and 350 ft²/gal so you are less likely to run short.
The coverage filled in for each type of paint is on the safe side: 8 m²/L for exterior paint, 5 m²/L for textured paint, 12 m²/L for enamel and 7 m²/L for primer.
Paint calculation example
A 4 m × 3 m room with 2.5 m walls, one 900 mm × 2,100 mm door and one 1,200 mm × 1,200 mm window has 31.67 m² of wall to paint.
Two coats at 10 m²/L needs 6.33 L — 3 tins of 2.5 L.
How much paint for a room: quick tables
| Room (floor size) | Wall height | Wall area to paint | Paint (litres) | Paint (US gallons) |
|---|---|---|---|---|
| 10 × 10 ft | 8 ft | 288 ft² | 6.23 L | 1.65 gal |
| 10 × 10 ft | 10 ft | 368 ft² | 7.96 L | 2.1 gal |
| 10 × 12 ft | 8 ft | 320 ft² | 6.92 L | 1.83 gal |
| 10 × 12 ft | 10 ft | 408 ft² | 8.83 L | 2.33 gal |
| 12 × 12 ft | 8 ft | 352 ft² | 7.61 L | 2.01 gal |
| 12 × 12 ft | 10 ft | 448 ft² | 9.69 L | 2.56 gal |
| 12 × 14 ft | 8 ft | 384 ft² | 8.31 L | 2.19 gal |
| 12 × 14 ft | 10 ft | 488 ft² | 10.56 L | 2.79 gal |
| 15 × 20 ft | 8 ft | 528 ft² | 11.42 L | 3.02 gal |
| 15 × 20 ft | 10 ft | 668 ft² | 14.45 L | 3.82 gal |
| 3 × 3 m | 2.5 m | 26.7 m² | 5.33 L | 1.41 gal |
| 3 × 4 m | 2.5 m | 31.7 m² | 6.33 L | 1.67 gal |
| 4 × 5 m | 2.5 m | 41.7 m² | 8.33 L | 2.2 gal |
Walls only, 2 coats, one door and one window taken off. Rooms in feet: 350 ft²/gal, door 36 × 80 in, window 36 × 48 in. Rooms in metres: 10 m²/L, door 900 × 2,100 mm, window 1,200 × 1,200 mm. Add the ceiling, primer or your tin size in the calculator above.
| Type of paint | Metric | US |
|---|---|---|
| Wall or ceiling paint (emulsion, plastic emulsion, distemper) | 10 m²/L | 350 ft²/gal |
| Outside walls (weather paint) | 8 m²/L | 300 ft²/gal |
| Textured paint | 5 m²/L | 200 ft²/gal |
| Enamel or gloss (doors, windows, grills, wood) | 12 m²/L | 400 ft²/gal |
| Primer or sealer only | 7 m²/L | 300 ft²/gal |
The typical coverage the calculator fills in for each type — on the safe side. If your tin gives a figure, use that one.
Tips before you buy
- Buy all the tins at once and mix them together ("boxing") so the colour is even.
- Dark colours over light walls, or light over dark, often need an extra coat or a tinted primer.
- A Pakistani "gallon" is 3.64 L or 4 L, not a US gallon (3.79 L) — pick the tin size from the list.
- Keep a small amount for touch-ups, labelled with the room and colour code.
Frequently asked questions
How much does a litre of paint cover?
Usually 10–16 m² per coat on smooth, painted walls, less on new plaster, cement or rough surfaces. Always check the tin.
How much does a gallon of paint cover?
About 350–400 ft² per coat on smooth, primed walls. A Pakistani 3.64 L gallon covers about 36–50 m² (390–540 ft²) per coat, depending on the paint.
How many coats of paint do I need?
Two coats is standard. One coat can be enough when you refresh the same colour on a sound wall; a big colour change or a new wall usually needs three, or a primer and two coats.
Should I subtract doors and windows?
Yes — the calculator takes them off using their width and height. Set the number to 0 if a wall has none.
Do I need primer or putty?
On new plaster, cement or bare board, use a primer or a mist coat so the topcoats cover as the tin says. In Pakistan and India walls often get 1–2 coats of putty for a smooth finish, then primer, then the paint.
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Sources
- Coverage ranges: manufacturers' published figures — e.g. Dulux Trade Vinyl Matt (up to 17 m²/L), Sherwin-Williams (350–400 ft²/gal, primer 200–300), Berger Pakistan (12–16 m²/L), Asian Paints (2 coats 10–12 m²/L).
- Pakistani tin sizes: Berger (0.91 / 3.64 / 14.56 L), Dulux Pakistan and Nippon (1 / 4 / 16 L).
- Wall putty: Dulux Pakistan Interior Acrylic Putty (4–6 m²/kg), Birla White (20–22 ft²/kg).
Formulas last reviewed: September 30, 2026 ·How we check our formulas