A wall’s area is calculated as length × height. Ceilings and openings need a separate calculation and an agreed approach.
A home’s square metres usually describe the floor. For painting, you need to measure the surfaces to be painted: walls, ceilings or both. A 70 m² flat does not necessarily have 70 m² of walls, and using that figure in the wrong field changes the estimate.
Measure a rectangular room
- Measure each wall’s length and height in metres. Multiply the two measurements.
- Add up the areas of the walls you want to paint.
- If you include the ceiling, multiply the room’s length by its width and add it separately.
- Note doors, windows and excluded areas to agree how they will be treated in the quote.
Calculation example, without deducting openings: a room measuring 4 × 3 metres and 2.5 metres high has two walls of 10 m² and two of 7.5 m². The walls total 35 m². The ceiling measures 12 m². If all these surfaces are painted, the geometric total is 47 m². The example assumes rectangular walls, uniform height and no sloping areas.
Do not convert the measured area into a universal quantity of paint. Before buying materials, check the coverage and application conditions of the product to be used.
When the room has an irregular shape
Divide an irregular wall into sections you can measure and add their areas. Keep sloping sections or measurements you cannot verify separate. If you only want to paint an accent wall, count that wall rather than the whole room.
When requesting a quote, provide your measurements table and explain whether you have deducted openings. Do not assume that every company uses the same method. Also state whether ceilings are included: this helps check the measurements and understand the proposal.
Record measurements together with their conditions
Use one row per room and record walls and ceiling separately. Add a notes column for openings, different heights or areas you do not want painted. If a measurement is still pending, mark it rather than copying another room’s. When the company reviews the home, you can compare its measurements with yours and locate any difference. If you rounded figures, explain that approach too. The company must confirm its measurement approach and whether it needs to visit the home.