Paint calculator
Work out how many litres of paint a room or feature wall needs after doors and windows, and which tins to buy.
Floor to ceiling. 2400 mm is 2.4 m.
A whole number. At least 2; dark colours can need more and a bright white can take 3.
Results
- Paint needed
- 4.1 LCoats: 2, spread rate 16 m²/L
- Area to paint
- 32.9 m²
- Tins to buy
- 1 × 4 L + 1 × 1 L0.9 L left over
Spread rate, door and window sizes
Use the spread rate on the back of your tin. Rough or porous surfaces take more paint.
Every door and every window is counted at these sizes. Measure one of each, architraves included if you will not paint them.
Tins in the mix: 1 L, 2 L, 4 L, 10 L, 15 L. The mix is the fewest tins that hold enough paint without leaving more than a 2 L tin over.
Estimate only. Check product labels and the building rules in your state or territory before you buy or build.
Quick answer
Multiply the room perimeter by the wall height, take off the doors and windows, multiply by the number of coats and divide by the spread rate on the tin, as a general guide about 16 m² per litre. A 4 × 3.5 m room with 2.4 m walls, one door and one window has 32.9 m² of wall, so two coats take 4.1 litres: a 4 L tin and a 1 L tin.
How to use the paint calculator
- Choose Room size and type the floor length and width and the wall height in metres, or choose Wall area for a feature wall or any walls you have already measured.
- Enter the number of doors and windows. Each door counts as 820 × 2040 mm and each window as 1200 × 1200 mm. Both are starting examples, so measure yours and change them under Spread rate, door and window sizes.
- Set the number of coats and choose Walls and ceiling if you are painting the ceiling too. The ceiling gets its own tins, so you can buy ceiling paint or a different colour for it.
- Check the spread rate on the back of your tin. The calculator starts at 16 m² per litre, the general guide Dulux gives for its wall, trim and ceiling paints.
How do you work out how much paint you need?
Find the wall area, take off the doors and windows, multiply by the number of coats and divide by the spread rate per litre. For a rectangular room the wall area is the perimeter, 2 × (length + width), times the wall height. Door and window sizes in centimetres become square metres when you divide width × height by 10,000.
The suggested tins are the fewest that hold enough paint without leaving more than one 2 L tin over. So 4.1 litres becomes a 4 L and a 1 L tin, 5 litres becomes a 4 L and a 2 L tin, and 8 litres becomes one 10 L tin.
wall area = 2 × (length + width) × wall heightdoor area (m²) = width (cm) × height (cm) ÷ 10,000area to paint = wall area − doors × door area − windows × window areaceiling area = length × widthpaint (litres) = area to paint × coats ÷ spread rate (m² per litre)How much paint do I need for a room?
A 4 × 3.5 m room with 2.4 m walls, one door and one window needs 4.1 litres for two coats on the walls: a 4 L tin and a 1 L tin. Every row below uses the same assumptions: 2.4 m walls, one 820 × 2040 mm door, one 1200 × 1200 mm window, two coats and 16 m² per litre.
| Room (m) | Walls (m²) | Paint (litres) | Tins, one of each |
|---|---|---|---|
| 3 × 3 | 25.7 | 3.2 | 4 L |
| 3.5 × 3 | 28.1 | 3.5 | 4 L |
| 4 × 3.5 | 32.9 | 4.1 | 4 L + 1 L |
| 4.5 × 3.5 | 35.3 | 4.4 | 4 L + 1 L |
| 5 × 4 | 40.1 | 5.0 | 4 L + 2 L |
| 6 × 4 | 44.9 | 5.6 | 4 L + 2 L |
Walls only, computed with the calculator. Ceilings add 1.1, 1.3, 1.8, 2.0, 2.5 and 3.0 litres for the same rooms: one 2 L tin up to 4.5 × 3.5 m, one 4 L tin for the two larger rooms.
Worked examples
A 4 × 3.5 m bedroom, walls and ceiling
The walls are 2 × (4 + 3.5) × 2.4 = 36 m². One door (82 × 204 cm = 1.67 m²) and one window (120 × 120 cm = 1.44 m²) leave 32.9 m² to paint. Two coats at 16 m² per litre take 32.9 × 2 ÷ 16 = 4.1 litres, so buy a 4 L tin and a 1 L tin, with 0.9 litres left over.
The ceiling is 4 × 3.5 = 14 m². Two coats take 14 × 2 ÷ 16 = 1.75 litres, one 2 L tin. In all you paint 46.9 m² with 5.9 litres.
A feature wall in a dark colour
A feature wall 4 m wide and 2.4 m high is 9.6 m². Choose Wall area, enter 9.6 and set Doors and Windows to 0. Dark colours can need more than two coats, so set Coats to 3: 9.6 × 3 ÷ 16 = 1.8 litres, one 2 L tin with 0.2 litres left over.
With two coats the same wall takes 1.2 litres, which is still one 2 L tin, as a 1 L tin would run short.
How many square metres does a litre of paint cover?
As a general guide, 1 litre of Dulux wall, trim or ceiling paint covers about 16 m², according to Dulux Australia, which also tells you that the coverage rate is per coat and printed on the back of the tin. At 16 m² per litre, a 4 L tin covers about 64 m² in one coat, or 32 m² with two.
| Tin | One coat covers | Two coats cover |
|---|---|---|
| 1 L | about 16 m² | about 8 m² |
| 2 L | about 32 m² | about 16 m² |
| 4 L | about 64 m² | about 32 m² |
| 10 L | about 160 m² | about 80 m² |
| 15 L | about 240 m² | about 120 m² |
Tin sizes from Dulux’s Wash&Wear Low Sheen interior paint, which is sold in 500 mL, 1, 2, 4, 10 and 15 L. The calculator leaves the 500 mL tin out of the mix.
How many coats of paint do I need?
At least two. Dulux Australia recommends at least two coats for a good finish and a minimum of two for dark colours, which may need more to reach the chosen colour. For whites it says two coats, or three for a bright finish.
Set Coats to 3 for a dark feature wall or a bright white, and the calculator scales the litres and the tins with it. For a primer, sealer or undercoat, work it out on its own with Coats set to 1 and the spread rate printed on that product.
Common questions
How much paint do I need for a bedroom?
About 4.1 litres for the walls of a 4 × 3.5 m bedroom with 2.4 m walls, so a 4 L tin and a 1 L tin. After one door and one window there are 32.9 m² to paint, and two coats at 16 m² per litre take 4.1 litres. Painting the 14 m² ceiling as well takes 1.75 litres more, which is one 2 L tin.
How many square metres does 4 litres of paint cover?
About 64 m² in one coat, or 32 m² with two, at the general guide of 16 m² per litre that Dulux Australia gives for its wall paint. That is enough for two coats on the walls of a 3.5 × 3 m room with one door and one window, which have 28.1 m² to paint and take 3.5 litres. Check the spread rate on your own tin.
How much paint do I need for a ceiling?
About 1.75 litres for a 4 × 3.5 m ceiling, so one 2 L tin. The ceiling is 14 m², and two coats at 16 m² per litre take 1.75 litres. Dulux gives the same general guide of about 16 m² per litre for its ceiling paint. To work out your own, multiply the room length by its width, then by the number of coats, and divide by the spread rate.
How much paint do I need for a feature wall?
One 2 L tin covers a feature wall 4 m wide and 2.4 m high. The wall is 9.6 m², so two coats at 16 m² per litre take 1.2 litres and three coats take 1.8 litres. Dark colours can need the third coat. Choose Wall area in the calculator, enter the wall’s area and set Doors and Windows to 0.
Where do I find the spread rate of my paint?
On the back of the tin, Dulux Australia says. Enter it in square metres per litre under Spread rate, door and window sizes. If your tin says 12 m² per litre, the 32.9 m² of walls in a 4 × 3.5 m room take 5.5 litres for two coats instead of 4.1, which is a 4 L tin and a 2 L tin.
Sources
- Dulux Australia, Guide to Painting Preparation (checked 19 October 2026)Paint needed comes from the wall area, the coverage rate on the can and the number of coats; the coverage rate is per coat, for example 12 m² per litre.
- Dulux Australia, Wash&Wear® Range (checked 19 October 2026)1 L of Dulux wall, trim or ceiling paint covers approximately 16 m² as a general guide; check the spread rate on the back of the can; at least two coats, dark colours may need more, whites 2 coats or 3 for a bright finish.
- Dulux Australia, Wash&Wear® Low Sheen (checked 19 October 2026)Sold in 500 mL, 1 L, 2 L, 4 L, 10 L and 15 L; apply two coats.
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