Build & renovate
Plaster Coverage Calculator
Coverage per bag is set by coat thickness: a bag that skims 10 square metres disappears into 3 as an undercoat.
Calculator
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How it works
Manufacturer averages: multi-finish skim ~10 m2 per 25 kg bag at 2 mm; bonding undercoat ~3 m2 at 8 mm; one-coat ~2.25 m2 at 10 mm. The tool adds 10% wastage and rounds up to whole bags.
Frequently asked questions
How many bags of multi-finish per room?
A 3 x 4 m room with 2.4 m ceilings has ~33 m2 of wall: four bags of skim finish with wastage - plus the ceiling if you are doing it.
How long does plaster stay workable?
Multi-finish gives you roughly 45 minutes to an hour from mixing. Mix what you can apply - a hardened bucket is a lost bag.