About this calculator
How much paint a room needs, split into wall and ceiling paint, with sensible tin sizes so you don’t overbuy.
How it’s calculated
Paint = area × coats ÷ coverage. Plascon gives a theoretical spread rate of 12 m² per litre for Double Velvet (interior) and Wall & All (exterior), on smooth, sealed surfaces. South African tins are 1, 5 and 20 litres. Doors and windows are deducted at standard sizes.
Worked example
With these inputs:
- Room length
- 4.2 m
- Room width
- 3.6 m
- Wall height
- 2.4 m
- Doors
- 1
- Windows
- 2
- Paint the ceiling
- Yes
- Coats
- 2
- Coverage (m² per litre)
- 12
- Add a plaster primer (new plaster)
- No
the result is:
- Wall paint
- 5.4 L
- Wall area (net)
- 32.54 m²
- Ceiling area
- 15.12 m²
- Primer
- 0 L
Tips from the trade
- Seal new plaster with a plaster primer before the top coats.
- Rough, textured or dark surfaces can drop coverage by 20–30%.
- Big colour changes (dark to light) usually need a third coat.
Common questions
How much paint for a 3.6 × 3.6 m room?
With 2.4 m walls, one door, two windows and two coats at 12 m² per litre, about 5 litres for the walls and 2.2 litres for the ceiling: a 5 L tin of wall paint and three 1 L tins of ceiling paint.
Results are estimates for planning and pricing. Check quantities against your drawings, the manufacturer’s data and SANS 10400 (the National Building Regulations) and your local municipality before ordering.