Room Paint Calculator — Litres, Coats & Coverage
Calculate how many litres of paint you need for a room — walls and ceiling. Enter room dimensions and number of coats, and the calculator accounts for window and door areas, paint coverage rate and whether you're painting over a similar or contrasting colour.
How the room paint calculator works
- 1Enter the net paint area directly, or calculate wall area manually as perimeter × height minus windows and doors before using the shared paint calculator
- 2For ceilings, calculate ceiling area separately and either run a separate paint calculation or add it to the total area if using the same paint and coat count
- 3Total area is the net area you enter; include ceiling area only if you have calculated it and it uses the same paint/coats/coverage
- 4Litres per coat = total area ÷ coverage rate (typically 10–12 m²/L for emulsion)
- 5Total litres = litres per coat × number of coats
- 6Round up to nearest tin size (typically 2.5 L, 5 L or 10 L)
Worked example
Bedroom: 3.6 m × 4.2 m, 2.4 m high. Two windows (1.2×1.2 m each), one door (0.9×2.0 m). 2 coats on walls, 1 coat on ceiling.
Wall area: 37.4 m² − 4.7 m² openings (2.88 + 1.80 m²) = 32.7 m². Ceiling: 15.1 m². Walls: 32.7 ÷ 11 × 2 = 5.9 L. Ceiling: 15.1 ÷ 11 = 1.4 L. Total: ~7.3 L → 1× 5 L + 1× 2.5 L.
Frequently asked questions
How many litres of paint do I need for a room?
A typical 12 m² bedroom (walls + ceiling) needs approximately 5–7 litres for 2 coats of emulsion at 11 m²/L coverage. Use the calculator above to get exact quantities for your room dimensions and number of coats.
How many coats of paint do I need?
2 coats is standard for most walls. 3 coats are needed when changing from a dark to a light colour, painting over bare plaster, or using highly pigmented feature colours. Always apply a primer coat on new plaster or bare surfaces.
What coverage rate should I use for paint calculations?
Standard emulsion wall paint: 10–12 m²/L per coat. Ceiling paint: 10–14 m²/L (smoother surface). Masonry paint: 5–8 m²/L (absorbent surface). Always check the specific product datasheet for the manufacturer's stated coverage.
Should I paint the ceiling or walls first?
Always paint the ceiling first. Work from back to front and top to bottom. Cut in (brush) the edges before rolling large areas. Let the ceiling fully dry before starting walls — this prevents drips landing on freshly painted walls.
Do I need to prime before painting a room?
New plaster and bare drywall must be primed — they absorb paint unevenly without primer. Previously painted walls in good condition typically don't need primer unless changing colour dramatically or repairing patches.