How this calculator works
The calculator uses the same method professional painters use to estimate a job:
- Wall area — for a room, that's the perimeter times the ceiling height: (Length × Height × 2) + (Width × Height × 2).
- Subtract openings — 2 m² per door and 1.5 m² per window.
- Multiply by coats — two coats means painting the area twice.
- Divide by the coverage rate — how many m² one litre covers on that surface (table below).
- Add 10% — for touch-ups, absorbent patches, and the paint that stays in the roller.
The result is rounded up to whole litres and converted into the tin sizes actually sold in South African hardware stores — 20 L, 10 L, 5 L and 1 L.
Coverage rates we use
Coverage depends on the surface — rough exterior plaster drinks far more paint than a smooth, sealed interior wall. These are the rates behind the calculator, based on manufacturer data sheets from Plascon, Dulux and Prominent:
| Paint type | Coverage per litre (per coat) | Notes |
|---|---|---|
| Interior wall paint (PVA / acrylic) | 8–10 m²/L | Smooth, previously painted plaster |
| Exterior wall paint | 6–8 m²/L | Rough or bagged plaster absorbs more |
| Primer / plaster sealer | 10–12 m²/L | One coat on new or stained surfaces |
| Deck coating / sealer | 4–6 m²/L | Bare timber is very absorbent |
| Textured paint | ~25% less than smooth | The texture itself holds extra paint |
Common South African room sizes
Don't have a tape measure handy? These are typical dimensions in South African homes — use them as a starting point and refine later:
| Room | Typical size | Paint needed (walls, 2 coats) |
|---|---|---|
| Single bedroom | 3 m × 3 m × 2.4 m | ± 6–7 litres |
| Main bedroom | 4 m × 3.5 m × 2.4 m | ± 8 litres |
| Living room | 5 m × 4 m × 2.6 m | ± 10–11 litres |
| Open-plan living / dining | 7 m × 5 m × 2.6 m | ± 14–15 litres |
| Kitchen | 4 m × 3 m × 2.4 m | ± 7 litres |
| Bathroom | 2.5 m × 2 m × 2.4 m | ± 4–5 litres |
Standard ceiling height in most South African homes is 2.4 m; older homes and modern open-plan builds often run 2.6–3 m. When in doubt, use 2.5 m.
What paint costs in South Africa (2026)
The cost estimate in the calculator uses these 2026 retail price bands. Prices are per 5-litre tin at builders' merchants and hardware stores in the Western Cape:
| Tier | Brands | Approx. cost (5L) | Best for |
|---|---|---|---|
| Budget | House brands, generic PVA | R160 – R240 | Rentals, outbuildings, touch-ups |
| Mid-range | Dulux, Prominent, Alcolin | R280 – R420 | Interior repaints, everyday quality |
| Premium | Plascon, Dulux Weatherguard, Micatex | R420 – R650 | Exteriors and long-lasting finishes |
| Roof / waterproofing | Plascon Nuroof, Prominent Roof, Sika | R480 – R750+ | Roofs and below-DPC walls |
Example projects
Repainting a standard bedroom (3 m × 3 m)
Walls: (3 × 2.4 × 2) + (3 × 2.4 × 2) = 28.8 m², minus one door (2 m²) and one window (1.5 m²) = 25.3 m². Two coats = 50.6 m² of painting. At 9 m²/L plus 10% extra: about 6–7 litres — one 5 L tin plus a 1 L or two. Add ± 2 litres if you're doing the ceiling.
Exterior of a 3-bedroom single-storey house
A typical 3-bed house has around 40 m of exterior wall at 2.7 m high = 108 m², call it 100 m² after openings. Two coats of exterior paint at 7 m²/L plus 10%: about 32 litres — one 20 L, one 10 L and a couple of litres spare. On rough or previously unpainted plaster, budget closer to 40 litres.
Sealing a 5 m × 4 m timber deck
20 m² of bare timber at 5 m²/L, two coats plus 10%: about 9 litres of deck sealer — two 5 L tins with a little left over for next season's maintenance coat.