About this calculator
Enter the area, thickness and mix.
How to use it
- Enter the area.
- Choose thickness and mix.
- Read cement and sand.
The formula
Wet volume = area × thickness; dry = wet × 1.33
- area
- wall or ceiling area to plaster
- mix
- 1:4 to 1:6 cement : sand
Worked example
1,000 sq ft of 12 mm plaster at 1:6
- Wet volume = 92.9 m² × 0.012 m = 1.11 m³.
- Dry = 1.48 m³; cement = 6.1 bags; sand = 1.27 m³ (44.9 cft).
What the result means
Rough brick walls take more plaster than smooth block walls; the 1.33 factor allows some extra.
Assumptions
- Even thickness.
Limitations
- Very uneven walls can need much more.
Frequently asked questions
How many bags of cement for 100 sq ft of plaster?
About 0.6 bags for 12 mm at 1:6.
What thickness for outside walls?
About 20 mm, in two coats.
Which sand for plaster?
Fine, clean plastering sand.
Last reviewed on 3 October 2026. Found a mistake? Tell us.