Plaster Calculator
Your estimate
Bags · 25 kg bags1
- Weight
- 52.7 lb23.9 kg
- Area
- 96 ft²10.67 yd² · 8.92 m²
Finish plaster (skim coat) or undercoat by thickness — bags for each wall or room.
Updated 2026-10-20 · Based on: coverage figures from paint and drywall makers (USG).
How to use the Plaster Calculator
- Enter the wall length and height.
- Choose finish (2 mm skim) or undercoat (8–11 mm).
- Pick the bag size and keep 10 % extra.
Formula
Plaster (kg) = area × thickness (mm) × consumption. Finish plaster about 1.2 kg per m² per mm; undercoat about 0.8 kg per m² per mm.
A 25 kg bag of finish covers about 10 m² at 2 mm.
Worked example
With the values preset in the calculator above:
- Length
- 12 ft
- Height
- 8 ft
- Thickness
- 0.08 in
- Plaster type
- Finish / skim coat
- Bag size
- 25 kg bags
- Extra for waste
- 10 %
- Bags
- 1
- Weight
- 52.7 lb (23.9 kg)
- Area
- 96 ft² (10.67 yd²)
Frequently asked questions
How much plaster for one wall?
A 4 × 2.4 m wall skimmed 2 mm thick needs 25.3 kg — 2 bag(s) of 25 kg.
How thick is a skim coat?
About 2–3 mm in two thin coats.
How long does plaster take to dry?
Skim coats dry in 1–3 days, thick undercoats a week or more — wait until it is evenly pale before painting.
More calculators
Estimates only — check quantities with your supplier and local building code before you order.