How much plaster do I need for a ceiling?

Ceiling plastering uses more material than walls due to overhead application losses. Multi-finish covers approximately 1.6 m² per 25kg bag on ceilings (compared to 1.8 m² on walls). For a standard 3.5m x 4m room (14 m²), you'd need around 10-11 bags of multi-finish including 15% wastage.

Is plastering a ceiling harder than walls?

Yes, ceiling plastering is significantly harder than walls. Working overhead causes more fatigue, more plaster falls off during application, and achieving a flat finish is more difficult. This is why we recommend 15% wastage for ceilings versus 10% for walls, and even more for DIYers.

Do I need bonding coat on a ceiling?

If your ceiling is bare concrete or very uneven, you'll need a bonding coat first (8-11mm), followed by a multi-finish skim coat (2-3mm). If you're skimming over existing plasterboard, you only need multi-finish. Artex ceilings being skimmed over typically just need multi-finish if the Artex is well-adhered.

How long does ceiling plaster take to dry?

Ceiling plaster typically takes 2-4 days to dry in normal conditions. The plaster will turn from dark pink/brown to a light, uniform pale colour when dry. Avoid heating the room artificially to speed drying — this can cause cracking. Ensure good ventilation instead.

What wastage should I allow for ceiling plastering?

Allow 15% wastage for experienced plasterers working on ceilings. For DIY ceiling plastering, allow 20-25% as the overhead working position means more material drops off. Ceiling work always generates more waste than wall plastering.

TradeCalcs

Ceiling Plaster Calculator — How Many Bags for Your Ceiling?

Calculate plaster needed for ceilings with adjusted coverage rates for overhead work. UK standard 25kg bags.

Ceiling Shape

Plaster Type

Ceiling Length

Main room length

Ceiling Width

Main room width

Include wastage allowance

Adds 15% extra for overhead application losses

Wastage Percentage

15% recommended for ceilings, 20-25% for DIY

Price Per Bag (optional)

Enter your supplier price for a cost estimate

How We Calculate This

Our ceiling plaster calculator uses adjusted coverage rates that account for the additional material loss when working overhead. Ceiling plastering has lower coverage per bag than wall plastering because gravity works against you — more plaster falls during application.

The formula

Bags needed = (Ceiling area ÷ Coverage per bag) × Wastage factor

For example, a 14 m² ceiling using multi-finish: 14 ÷ 1.6 = 8.75, rounded up to 9 bags, plus 15% wastage = 11 bags.

Ceiling coverage rates

Multi-Finish (Thistle): 1.6 m² per 25kg bag at 2mm (reduced from 1.8 m² on walls)
Bonding Coat: 1.4 m² per 25kg bag at 8mm thickness
One Coat: 1.8 m² per 25kg bag at 13mm thickness

Coverage rates are reduced by approximately 10-15% compared to wall application to account for overhead working losses. These rates are derived from British Gypsum guidelines with adjustments for real-world ceiling conditions.

Frequently Asked Questions

Related Calculators

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Skim Coat Calculator

Calculate multi-finish plaster needed for skim coating walls and ceilings.

Rendering Calculator

Calculate sand and cement quantities for external rendering.

Dot and Dab Calculator

Work out adhesive needed for dot and dab plasterboard fixing.

Last updated: February 2026

All calculations are estimates. Verify with your supplier.