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Ceiling Paint Calculator — How Much Ceiling Paint Do I Need?
Calculate paint needed for ceilings including mist coats for new plaster. Accounts for smooth, textured and Artex ceilings.
Longest dimension of the room
Shortest dimension of the room
Adds 10% extra for roller loading and drips
10% standard — ceilings can be messy to paint
Enter your supplier price for a cost estimate
Trade rule-of-thumb for a diluted mist coat on new plaster (default 8 m²/L) — not a datasheet figure; diluted paint spreads further but bare plaster is very absorbent
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How We Calculate This
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.
Frequently Asked Questions
Yes — a mist coat is essential on new plaster ceilings. New plaster is highly absorbent and will soak up undiluted paint unevenly, leaving a patchy finish. A mist coat is standard white emulsion thinned with water. A common decorator's mix is around 70% paint to 30% water, but always follow the tin — Dulux Trade Vinyl Matt's data sheet advises adding up to 1 part clean water to 5 parts paint (about 17% water) for the first coat on bare surfaces, while Dulux Trade Supermatt advises up to 1 part water to 3 parts paint (about 25%). This seals the plaster and provides a consistent base for top coats. Allow 24 hours for the mist coat to dry before applying top coats. For walls on new plaster, use our Primer Calculator for detailed quantities.
Textured and Artex ceilings have a much greater actual surface area than their flat dimensions suggest — the peaks, valleys and patterns create more surface to cover. There is no published manufacturer figure for this; as a working rule, light texture needs roughly 25-33% more paint than smooth (about 8-9 m²/L), while deep or heavy Artex can need up to double. This calculator uses a cautious 6 m²/L for textured ceilings so you don't under-order on heavy texture; you may have paint left over on a lightly textured ceiling. A long-pile roller (12-18mm) helps work paint into the texture.
A dedicated ceiling paint (such as Dulux Ceiling Paint or Crown Ceiling Paint) is recommended. Ceiling paints are formulated to be thicker and less prone to drips and spattering compared to standard emulsion. They typically dry to a flat matt finish which hides imperfections. For bathrooms and kitchens, use a moisture-resistant ceiling paint to prevent mould growth.
Two coats of ceiling paint is standard for a good finish on previously painted smooth ceilings. New plaster needs a mist coat first, then two top coats. When changing from a dark colour to a light one, you may need three coats. Textured or Artex ceilings may only need one thick coat if using a high-opacity ceiling paint, but two coats gives the best finish. For the walls in the same room, use our Paint Coverage Calculator.
For an L-shaped room, divide the ceiling into two rectangles. Calculate each rectangle separately (length x width) and add the areas together. Enter the total combined area into the calculator. For example, if one section is 3m x 4m (12 m²) and the other is 2m x 3m (6 m²), your total ceiling area is 18 m².
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Last updated: February 2026
Verified against UK standards · estimates only, confirm with your supplier.