handyfig
USUKAU

Paint Calculator (Litres)

Work out how many litres of paint a room needs, and which tins to buy. Every assumption is editable.

Room lengthRoom widthSeen from aboveDoorWindowWall heightOne wall
Key Where each paint measurement is taken.
Units
m
m
Typical ceiling. 2.4 m is common, and 2.7 m is common in newer homes. Editorial rule of thumb.
m
m²

If you fill this in, it is used instead of the room size for the walls.

Typical door. The most common internal door is 820 x 2040 mm, about 1.7 m². Taller 2340 mm doors are becoming more common in newer homes. Source: Doors Plus, listed below.
m²
Windows vary a lot. The starting figure is only a placeholder. Measure each window you will not paint.
m²
m²/L

Check the tin. The starting figure is cautious.

%
$

Adds an estimated cost for the suggested sizes.

Paintable area32.9 m²
Paint needed, 2 coats4.70 L
Paint to buy, with waste5.2 litres
Suggested tins1 × 4 L + 1 × 2 L (6 L)

Walls: 2 × (4 + 3.5) × 2.4 m = 36 m², minus doors and windows 3.1 m², gives 32.9 m² to paint. × 2 coats = 65.8 m²; ÷ 14 m²/L = 4.70 L; with 10% waste = 5.17 L.

Porous, rough or dark surfaces need more paint. Check the coverage on the tin.

Fig. 1 Paint for your room.

Every formula is tested against worked examples. How we check

CoatsPaint to buySuggested tins
1 coat2.59 L1 × 2 L + 1 × 1 L
2 coats5.17 L1 × 4 L + 1 × 2 L
3 coats7.76 L2 × 4 L

Fig. 2 The same room at one, two and three coats.

Last checked 10/11/2026. Sources: Dulux Australia: Paint calculator (16 m² per litre for wall, trim and ceiling paint, two coats); Doors Plus: Standard internal door sizes in Australia (820 x 2040 mm is the most common).

Guide

How the amount is worked out

Wall area = 2 × (length + width) × height. Take away the doors and windows, add the ceiling if you are painting it, multiply by the number of coats, then divide by how far a litre spreads. Finally add a little extra for waste.

Example. A 4 × 3.5 m room with 2.4 m walls has 36 m² of wall. One door (1.9 m²) and one window (1.4 m²) leave 32.7 m². Two coats make 65.4 m², and at 14 m² per litre that is 4.67 litres before waste, about 5.1 litres with 10% extra.

Where the 14 m² per litre comes from

Dulux Australia’s own paint calculator assumes two coats at 16 m² per litre for its wall, trim and ceiling paints and 14 m² per litre for its primer, and says coverage varies with the surface and the product. The tool starts a little lower, at 14, because real walls are rarely perfect. Rough or porous surfaces, new plasterboard and strong colour changes need more, so check the spread rate on your tin.

Common mistakes

  • Forgetting the second coat. Most rooms need two.
  • Buying exactly the figure shown. Keep a little for touch-ups.
  • Treating the door and window sizes as exact. They are averages; measure large windows and sliding doors and use the direct wall-area box.
  • Skipping the undercoat on bare plasterboard or a big colour change. That is a separate product with its own spread rate on the tin.

Pack sizes

The suggested tins use 1 litre, 2 litre, 4 litre and 10 litre sizes. The tool picks the least paint that covers the amount using the fewest tins. Sizes vary by brand, so treat it as a starting point.

Common questions

How many litres of paint for a 4 x 3.5 m bedroom?

With 2.4 m walls, one door, one window and two coats, a 4 x 3.5 m room needs about 4.7 litres at 14 m² per litre, or about 5.1 litres with 10% for waste. At Dulux’s 16 m² per litre the same room needs about 4.1 litres, so coverage is the big lever: check your tin.

Do I paint the door and window area?

No. The calculator subtracts them. If your windows are large or you have lots of trim, change the deduction.

Does the ceiling use the same paint as the walls?

Usually not; ceilings often take a ceiling paint. Run the tool once for the walls and once for the ceiling for separate quantities.

Can I use the same figure for exterior walls?

Not reliably. Render, brick and weatherboard soak up paint differently. Use the spread rate printed on your exterior paint tin.

Worked examples

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