Concrete Slab Calculator for Cement, Sand and Aggregate
Calculate concrete slab volume, dry mix, cement bags, sand, aggregate and waste allowance for construction material estimates.
Estimation Inputs
Surface area of the slab.
Concrete pour thickness.
Cement proportion in the mix.
Sand proportion in the mix.
Aggregate proportion in the mix.
Compaction and shrinkage factor.
Allowance for spill and site loss.
Weight of one cement bag.
Pricing & Rates
Price per purchase unit used by this calculator.
Applied to the estimated purchase quantity.
Use 0 if tax is not applicable.
Quantity Takeoff
wet Volume
10
total Wet Volume
10.5
dry Volume
16.17
cement Volume
2.31
Formula Trace
Slab Wet Volume:
Area * Thickness
100.00 m² * 0.100 m
= 10.000 m³
Wet Volume (with Waste):
Wet Volume * (1 + Wastage % / 100)
10.00 m³ * (1 + 5.0 / 100)
= 10.500 m³
Dry Mix Volume Required:
Wet Volume (with Waste) * Dry Volume Factor
10.50 m³ * 1.54
= 16.170 m³
Cement Dry Volume:
Dry Volume * (Cement Ratio / Ratio Sum)
16.17 m³ * (1 / 7)
= 2.310 m³
Cement Bags (50kg bags):
ceil((Cement Volume * Density 1440 kg/m³) / Bag Weight)
ceil((2.310 m³ * 1440) / 50 kg)
= 67.000 bags
Sand Dry Volume:
Dry Volume * (Sand Ratio / Ratio Sum)
16.17 m³ * (2 / 7)
= 4.620 m³
Coarse Aggregate Volume:
Dry Volume * (Aggregate Ratio / Ratio Sum)
16.17 m³ * (4 / 7)
= 9.240 m³
Estimate Outcome
Calculation guide and formulas
Use this concrete slab calculator to estimate wet volume, dry concrete mix volume, cement bags, sand and aggregate for slabs, footings and small pours.
Understand the units, allowances and purchase rounding (English).
Worked example
A 100 m² slab with 0.1 m thickness needs 10 m³ wet concrete. With 5% waste and a 1.54 dry factor, dry volume is 16.17 m³. For a 1:2:4 mix, cement is about 2.31 m³ or 67 bags.
Frequently asked questions
Q: Why use a dry volume factor for concrete?
A: Dry ingredients contain voids. A dry volume factor accounts for compaction and shrinkage when cement, sand, aggregate and water are mixed.
Q: Can this concrete calculator replace structural design?
A: No. It is for material estimation and planning. Structural grade, reinforcement and code requirements should be checked by a qualified professional.