Plaster calculator
Plaster consumption is roughly proportional to thickness: each centimetre on each square metre takes a fixed amount of dry mix. Enter the area, the average thickness and the bag size.
Your measurements
Result
- Dry plaster needed
- 1,020 kg
- Bags to buy
- 34 pcs
17 kg per m² per cm is typical for lime-cement plaster; gypsum plasters are lighter (about 10 kg/m² per cm).
How the calculation works
- Quantity (kg) = area × thickness (cm) × 17 kg — the usual dry-mix consumption per m² for each centimetre.
- Bags = kilograms ÷ bag size, rounded up.
Worked example
For 30 m² of 2 cm plaster: 30 × 2 × 17 = 1,020 kg, which is 34 bags of 30 kg.
What the calculator assumes
- 17 kg/m² per cm is typical for lime-cement plasters; gypsum plasters are lighter (about 10 kg/m² per cm).
- The thickness is the average — on uneven walls measure in several places.
When to adjust the result
- Indoors walls are usually plastered 1–1.5 cm thick, outdoors about 2 cm; over 2 cm the plaster goes on in two coats.
- Corner beads, plaster screeds and reinforcing mesh over cracks are not included.
Getting a good plaster finish
Background preparation decides adhesion. Remove loose material, dampen very absorbent masonry or apply the bonding agent the plaster manufacturer specifies, and fix angle beads on external corners before plastering. On mixed backgrounds — brick next to concrete — embed mesh over the joint to prevent cracks.
Apply in the thickness range on the bag; very thick coats need two passes. Protect fresh plaster from frost, direct sun and drafts so it does not dry too fast, and let it dry fully before painting — usually a few weeks, depending on thickness and ventilation.
Frequently asked questions
How much plaster per square metre?
About 17 kg per cm of thickness for lime-cement plaster, so roughly 25 kg for 1.5 cm. Gypsum plaster needs about 10 kg per cm.
How thick should wall plaster be?
Around 1–1.5 cm indoors and about 2 cm outdoors; thicker coats are applied in two passes.
Gypsum or cement-lime plaster?
Gypsum plaster is for dry interior rooms and gives a smooth finish; cement-lime plaster suits bathrooms, basements and exterior walls.
How long before I can paint new plaster?
Until it is fully dry and uniform in colour — often two to four weeks for normal thicknesses; follow the manufacturer's guidance.