Most people buy paint the way they buy rice: by eye, at the counter, and then go back for more. On a three-bedroom flat that second trip is usually avoidable, and the leftover tin in the store is the other half of the same mistake.
The number you need is not floor area. It is wall area, how many coats that wall takes, and how far a litre of the actual product spreads. Here is the whole calculation, worked through on a typical Nigerian three-bedroom flat.
Step one: measure the walls, not the floor
For each room, add the length of all four walls and multiply by the ceiling height. Then subtract the doors and windows, because you are not painting those.
A standard door is about 1.8 square metres. A standard window is about 1.5. A full-height window or a wide slider is more.
Here is a typical three-bedroom flat, 2.7 metre ceilings:
- Living room, 5m by 4m: perimeter 18m, so 48.6 square metres of wall, less one door and two windows, about 43 square metres
- Bedroom 1, 4m by 3.5m: perimeter 15m, less openings, about 36 square metres
- Bedroom 2, 3.5m by 3m: about 31 square metres
- Bedroom 3, 3m by 3m: about 28 square metres
- Kitchen, 3m by 2.5m: about 26 square metres
- Two bathrooms, 2m by 2m each: about 18 square metres each
That is roughly 200 square metres of wall, and about 69 square metres of ceiling if you are doing those too.
Step two: decide how many coats
Two coats is the normal answer. One coat is only enough when you are refreshing the same colour over a sound, clean wall, and even then it usually looks thin where light rakes across it.
- Same colour, good condition — one coat, occasionally two
- Colour change, sound wall — two coats
- Dark colour going lighter — budget three, and expect the first to look worrying
- New plaster — a sealer or primer, then two coats. New plaster drinks paint unevenly and will show every patch if you skip the primer
Step three: divide by the coverage on the tin
Coverage is printed on the tin and on the technical data sheet, and it varies between products. A typical emulsion covers somewhere between 10 and 12 square metres per litre per coat. Use the number for the product you are actually buying, not this one.
At 11 square metres per litre:
- Walls: 200 square metres, two coats, is 400 square metres of paint film. Divided by 11, that is 36 litres
- Ceilings: 69 square metres, two coats, is 138. That is 13 litres
So a three-bedroom flat is roughly 36 litres on the walls and 13 on the ceilings — call it a 20 litre tin plus four 4 litre tins for the walls, and four 4 litre tins for the ceiling.
Step four: add the waste
Add 10 per cent. Some paint stays in the tin, some goes on the roller and never reaches the wall, textured surfaces take more than flat ones, and porous new plaster takes a lot more.
That takes the walls to about 40 litres and the ceilings to about 14. If the walls are textured, or the flat has been repainted many times and the surface is rough, add 15 per cent instead.
What changes the answer
- Textured or rough walls — more surface, more paint. A heavy texture can absorb 20 to 30 per cent more
- POP ceilings — take their own product and their own calculation; they are not the same job as a plastered ceiling
- Doors, frames and skirting — gloss work is usually quoted separately and is measured in linear metres, not square metres
- Primer and filler — count these as a separate line. Primer is cheaper per litre than topcoat but you still need it
Buying it
Buy the whole job in one go where you can. Paint mixed in different batches can vary slightly in shade, and a wall painted from two batches sometimes shows the join.
Tell us the room sizes and the ceiling height and we will work the quantities for you against the actual product. Call +234 802 562 5333, message WhatsApp, or send your project details.
For the walls in this calculation, see Prestige Matt Finish and Prestige Satin Finish. For the ceilings, Prestige Best for POP.