PLASTER
Plaster Calculator: Cement and Sand for Plastering
Calculate cement bags and sand for 6, 12, 15 or 20 mm plaster in 1:3 to 1:6 mixes, with dry-volume and wastage allowances shown.
Assumptions used EDIT ▾
Commonly 1.27.
%
Wet mortar = area × thickness. Dry volume = wet volume × the dry factor (sand and cement bulk before mixing), plus an allowance for uneven surfaces and wastage. Cement is converted at 1,440 kg/m³ and 50 kg per bag.
CEMENT
7bags
6.1 × 50 kg bags
- Sand1.27 m³
- 45 cft
- Dry mortar1.11 m³ wet
- 1.49 m³
Cement7 bags
How it’s calculated
Dry mortar = area × thickness × 1.27 (+ wastage); cement = dry ÷ (1 + n) × 1440 ÷ 50
Example: 100 m² at 12 mm in 1:6: wet 1.2 m³ → dry ≈ 1.6 m³ → ≈ 6.6 bags.
Estimates for planning, based on the assumptions shown. They are not a guarantee of quantities or professional engineering advice; check critical work with a qualified professional.