Use this free concrete volume calculator to find the wet and dry volume of concrete and the quantity of cement (bags), sand and aggregate for a slab, beam or column using standard mix ratios (M15, M20, M25).
Concrete Volume Calculator
Formula
Wet volume = Length × Width × Thickness. Dry volume = Wet volume × 1.54. Materials are split by the mix ratio, and cement bags = cement volume ÷ 0.0347 m³ (one 50 kg bag).
How to Use This Calculator
- Enter the length, width and thickness in metres.
- Select the concrete mix ratio (M15, M20 or M25).
- Click Calculate to get wet/dry volume and cement, sand and aggregate quantities.
Worked Example
For a slab 5 × 4 × 0.15 m in M20 (1:1.5:3): wet volume = 3 m³, dry volume = 4.62 m³, giving about 24 cement bags, 0.84 m³ sand and 1.68 m³ aggregate.
Frequently Asked Questions
How do you calculate concrete volume?
Multiply length x width x thickness for the wet volume, then multiply by 1.54 to get the dry volume used for material estimation.
Why multiply concrete volume by 1.54?
Dry materials (cement, sand, aggregate) occupy more space than the final set concrete, so a dry-volume factor of about 1.54 is applied.
How many cement bags are in 1 m3 of concrete?
It depends on the mix; for M20 (1:1.5:3) roughly 8 bags of cement are needed per cubic metre of wet concrete.