Painting
Paint Calculator
Enter your room size and we will tell you how much paint to buy, including the tins to pick up.
Results update as you type. Nothing to sign up for.
Measurements
Switch between metric and imperial at the top of the form.
Floor to ceiling.
Adds the floor area to the area being painted.
Material
Two coats give even colour on most walls.
Printed on the tin. Around 10 m²/L for emulsion.
You need approximately
7.5L
of paint to buy
Area to paint
29m²
Coats
2
Coverage
10m²/L
Waste allowance
10%
Your measurements
- Room perimeter
- 14 m
- Wall area
- 33.6 m²
- Doors and windows deducted
- -4.6 m²1 door, 2 windows
- Area to paint
- 29 m²
How much paint
- Total area over 2 coats
- 58 m²
- Paint needed
- 5.8 L
- With 10% waste
- 6.38 L
- What to buy
- 1 × 5 L + 1 × 2.5 L7.5 L in total
What to buy
Paint
1 × 5 L + 1 × 2.5 L
7.5 L total
Want a cost too?
Add your prices in the cost section of the form. We never guess prices — a made-up figure is worse than none.
How to work out how much paint you need
- Measure the length and width of the room, and the height from floor to ceiling.
- Add the two lengths and two widths together to get the perimeter, then multiply by the height. That is your wall area.
- Subtract the doors and windows — about 1.8 m² for a door and 1.4 m² for a window.
- Multiply by the number of coats you plan to apply. Two is normal.
- Divide by the coverage printed on the tin, usually around 10 m² per litre.
- Add about 10% for waste, then round up to the tin sizes your shop sells.
The paint formula
Perimeter = (length + width) × 2
Wall area = perimeter × wall height
Area to paint = wall area (+ ceiling) − doors − windows
Total area = area to paint × number of coats
Litres = total area ÷ coverage × (1 + waste %)
Example: a 4 × 3 m room with 2.4 m ceilings
The perimeter is 14 m, so the wall area is 33.6 m². Take off one door (1.8 m²) and two windows (2.8 m²) and you have 29 m² to paint. Two coats makes 58 m². At 10 m² per litre that is 5.8 litres, and with 10% waste 6.38 litres — so you buy one 5 litre tin and one 2.5 litre tin, 7.5 litres in all.