Estimate cement and sand for the specified layer using square feet or m². Adjust the mix, factors and material allowances.
How to use this tool
Enter your values and calculate a result. Check the units and assumptions before using the estimate.
Surface area
Input unit
Output units
Layer thickness
Thickness unit
Dry volume factor
Cement mix parts
Sand mix parts
Cement bag volume (CFT)
Cement bag mass (kg)
Roof fill layer depth (feet)
Cement allowance (%)
Sand allowance (%)
Roof fill allowance (%)
Polythene coverage allowance (%)
Bitumen coverage allowance (%)
Material estimates use editable template assumptions. Cement bags assume 50 kg and 1.25 CFT per bag by default; adjust both for your product. Allowances are applied independently to each material. Structural steel percentages are preliminary quantities, not reinforcement design. Bitumen output is treatment coverage area, not product litres or kilograms. Product consumption must come from its manufacturer.
How to use this calculator
Enter the measured quantity, choose the input unit and select your preferred output units. Open the mix and allowance settings to adapt the estimate to your materials and project.
Formula and assumptions
The calculation uses the following editable defaults. They are estimating assumptions, not a universal construction standard.
Measured volume
Default mix (cement : sand : aggregate)
Dry volume factor
1:4:0
Layer thickness (inches)
1.42
Assumed cement bag mass
1.25 CFT
Allowance
50 kg
Mortar fraction
1
V = measured volume in CFT; area input = square feet; D = dry material volume in CFT. In mix fractions C, S and A mean cement, sand and aggregate parts.
D = A × (1 / 12) × 1.42
Cement bags = D × C / (C + S + A) / 1.25
Sand (CFT) = D × S / (C + S + A)
Roof fill (CFT) = Area (sq ft) × 0.167
Worked example
The example uses 100 CFT or 100 square feet, as appropriate. Base quantities match the template method. Each allowance is applied to its own material.
Material
Base quantity
With allowance
Cement
1.893333 bags
1.988 bags
Sand
9.466667 cft
11.833333 cft
Roof fill
16.7 cft
25.05 cft
Polythene coverage
100 sqft
110 sqft
Bitumen coverage
100 sqft
115 sqft
Frequently asked questions
Can I enter metric quantities?
Yes. The tool converts m³ to CFT or m² to square feet before applying the same material formula. Selecting metric outputs converts material volumes and coverage areas back to m³ and m².
Does this specify a structural design?
No. Mix ratios, layer thicknesses and steel percentages are editable estimating inputs. Follow approved drawings, product specifications and the local requirements for your project.
What does the rounded purchase quantity mean?
Brick, brick tile and cement bag purchasing quantities round up after their individual allowances. The unrounded base quantity is also shown so you can compare it with the source method.
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