Ceiling Paint Calculator — How Much Ceiling Paint Do I Need?

Our ceiling paint calculator works by multiplying room length by width to get the ceiling area, then dividing by the coverage rate for your ceiling type. For new plaster ceilings, it separately calculates the mist coat (diluted emulsion) and the top coats, as they have different coverage rates.

The formula

Ceiling area = Room length × Room width

Top coat litres = (Ceiling area × Number of coats) ÷ Coverage rate × Wastage factor

For new plaster: Mist coat litres = Ceiling area ÷ 8 m²/L × Wastage factor (applied as 1 coat)

For example, a 4m × 3.5m ceiling (14 m²) with smooth plaster, 2 coats at 12 m²/L: 14 × 2 ÷ 12 = 2.3 L, plus 10% wastage = 2.6 L. You'd need 2 × 2.5L tins.

For new plaster, add a mist coat: 14 ÷ 8 = 1.75 L, plus 10% = 1.9 L. Total = 2.6 + 1.9 = 4.5 L.

Coverage rates by ceiling type

• Smooth Plaster: 12 m²/L — a conservative working rate for a previously painted ceiling
• Textured / Artex: 6 m²/L — heavy-texture estimate; light texture often only needs ~8-9 m²/L
• New Plaster (mist coat): 8 m²/L — rule-of-thumb for diluted emulsion sealing bare plaster
• New Plaster (top coats): 12 m²/L — same conservative rate as a smooth ceiling once sealed

These are deliberately cautious working rates, not manufacturer headline figures. Brands publish higher spreading rates on smooth surfaces — Dulux retail Walls & Ceilings matt quotes up to 14 m²/L, and Dulux Trade Vinyl Matt and Crown Trade Matt Vinyl up to 17 m²/L. We use a lower 12 m²/L so the quantity errs on the safe side (slightly over rather than under). Actual coverage depends on the ceiling condition, porosity, colour change and application method. Use a roller for best results — a medium-pile roller (9-12mm) for smooth ceilings and a long-pile roller (12-18mm) for textured ceilings — and always check the spreading rate printed on your tin.