How much does a bag of plaster cover?

A 25 kg bag of gypsum plaster covers about 2.5–3 m² at 10 mm thickness — the rule of thumb is 1 kg per m² per millimetre of layer. Cement render is heavier: 17–20 kg per m² at 10 mm, so a 25 kg bag does just over 1 m².

Material (bag)	Consumption	Coverage per bag
Gypsum plaster 25 kg	~1.0 kg/m² per mm	2.5–3 m² @ 10 mm
Gypsum plaster 25 kg, skim 5 mm	~1.0 kg/m² per mm	5–6 m²
Cement render 25 kg	17–20 kg/m² @ 10 mm	~1.3 m²
Ready skim coat / filler 20 kg	1.0–1.2 kg/m² per mm	8–10 m² @ 2 mm
Tile adhesive 20 kg	3–5 kg/m² (6–8 mm trowel)	4–6 m²
Joint compound 20 kg	~0.35 kg/m² per joint layer	~55 m² of board

Why real coverage is lower than the label

Manufacturers quote coverage on a perfectly flat wall. Real walls eat 10–20% more: dips get filled, the first pass keys into the surface, and some mix always dries in the bucket. Buy one bag extra per 5–6 planned, and prime porous walls — primer cuts absorption and saves material.

🧮 Calculate plaster for your wall

Frequently asked questions

How many bags of plaster do I need per room?

Multiply wall area by thickness in mm to get kilograms (gypsum ≈ 1 kg/m²/mm), then divide by bag weight. A 12 m² wall at 10 mm needs ~120 kg — five 25 kg bags with a small reserve.

Does thickness change coverage proportionally?

Yes, linearly: 5 mm doubles the area per bag versus 10 mm, 20 mm halves it. That is why the layer thickness matters more than the bag brand when estimating.

How much does a bag of cement cover for rendering?

Mixed 1:4 with sand, a 50 kg cement bag yields roughly 8–9 m² of 10 mm render. The sand does most of the volume — cement is the binder, about 5–6 kg per m².

How much paint does a litre cover?

Around 8–12 m² per litre per coat on a smooth primed wall. Two coats are standard, so 1 litre finishes roughly 5 m² of wall completely.