← 🏠 Homeowners and DIYers toolkit
Room Paint Calculator
How much paint you need for a room, and how many tins to buy.
Part of the 🏠 Homeowners and DIYers toolkit, with more tools made for the job.
Leave empty for none.
Leave empty for none.
Leave empty for a typical door.
Leave empty for a typical window.
Leave empty for 2.
Printed on the tin. It changes with the paint and the wall.
Gives the number of tins.
Type the room size and the coverage from the tin, and the paint you need appears here.
Was this tool useful?
One click, no sign-up.
Type the room size, the number of doors and windows and the coverage printed on the tin. This works out the area you will paint and the amount of paint to buy.
Paint is easy to under-buy or over-buy, and the tin always seems to run out one wall short. The working is simple: find the wall area, take off the doors and windows, divide by what a litre or gallon covers, and multiply by the coats. This tool does that and rounds up to whole tins. The coverage figure is on the tin, because it changes with the paint and with how rough or porous the wall is.
How it’s worked out
- Wall area is the distance around the room (twice length plus width) times the wall height.
- Doors and windows are taken off. If you do not give their sizes, typical ones from decorating guides are used.
- Paint per coat is the area to paint divided by the coverage on the tin. Total paint is that times the number of coats.
- Tins are the total paint divided by the tin size, rounded up. Tick the ceiling to add its area.
A 4.5 m by 3.5 m room with 2.4 m walls, one door and one window has 38.4 square metres of wall and about 35 left after the openings. At 10 square metres a litre and two coats that is about 7 litres, so three 2.5 litre tins.
Common mistakes
- Using the wrong coverage. It is printed on the tin and changes with the paint, so do not use a general figure from a website.
- Forgetting a primer coat or a second coat. Dark colours, new plaster and bare wood often need more than two coats in total.
- Painting over rough or porous walls with a smooth-wall figure. Textured and thirsty surfaces use more paint.
- Leaving out skirting, doors and frames. Trim often needs a different paint, so work it out separately.
Questions
Where do I find the coverage?
On the tin or the maker's website. It is usually given as square metres per litre or square feet per gallon for one coat on a smooth, sealed surface.
How many coats do I need?
Two is the usual starting point. A big colour change, new plaster or bare wood can need more, and some paints are sold as one-coat. Follow the instructions on the tin.
What door and window sizes are used?
If you leave them empty, a door is taken as about 1.9 square metres (20 sq ft) and a window about 1.2 square metres (13 sq ft). Measure yours for a closer answer.
Does it work for a ceiling?
Yes. Tick the box and the room's floor area is added as ceiling. Paint for the ceiling is often a different one, so you may prefer to run it again by itself.
Where the method comes from
Estimates only
These are estimates and general information, not building, safety, legal or professional advice. Materials, coverage, waste and rules vary by product, project and place, so check the maker's instructions and your local rules, and use a qualified person for gas, electrical and structural work.
Rain stopped play. Officially research.