Concrete Calculator
Estimate cement bags, sand and aggregate for slabs and footings.
A 10×10 ft slab, 4 inches thick is ~33 cubic feet of concrete — at M20 (1:1.5:3) that’s about 7–8 bags of cement, ~15 cft sand and ~30 cft aggregate. Order 5–10% extra; running short mid-pour creates weak cold joints.
How to use the concrete calculator
- Enter length, width and thickness.
- Pick the mix ratio.
- Get cement bags, sand and aggregate.
Concrete Calculator — FAQs
What do M15/M20 mean?
The ‘M’ grade is compressive strength in MPa at 28 days: M15 (1:2:4) for plain work, M20 (1:1.5:3) for reinforced slabs and columns.
How many cement bags per cubic metre?
Roughly 6.5–7 bags for M20. A 50 kg bag is ~1.225 cubic feet of cement.
Why add extra material?
Dry volume exceeds wet volume by ~52% (voids between aggregates) — the calculator accounts for this; the extra 5–10% covers spillage.
Can I mix by hand for small work?
For small patches yes, but machine mixing gives far more uniform strength. Never hand-mix structural columns.
Keep exploring
People who used this also opened:
Tile Calculator →
Calculate floor tiles needed — including 10% wastage.
homePaint Calculator →
Estimate paint needed for any room — litres, coats and cost.
convertVolume Converter →
Convert between litres, millilitres, gallons, cups and cubic metres.
convertArea Converter →
Convert between sq ft, sq m, acres, hectares and more.