Concrete calculator
Concrete volume, cement bags, sand and aggregate for slabs, footings and columns.
How it is calculated
Wet volume = length × width × thickness (× count). Dry volume = wet volume × dry factor (1.54 by default, allowing for voids and bulking). Cement = dry volume × cement part ÷ total parts × 1,440 kg/m³ ÷ bag size. Sand and aggregate = dry volume × their parts ÷ total parts.
Check locally: The dry factor, cement density and bag size are common assumptions you can edit. Use a designed mix for structural work.
Questions
Why multiply by 1.54?
Dry materials shrink when mixed with water and fill voids, so about 54% more dry volume is needed. You can change this factor.
Is anything I enter saved or sent?
No. The calculation runs in your browser. Nothing you type is sent anywhere. You can copy the result, print it or download it as a CSV.