Calculator
Concrete Mix Ratio Calculator
Enter your slab or footing size and concrete grade to get cement, sand, and aggregate quantities. Pick M10–M30 — each grade uses a fixed mix ratio.
Inputs
Unit system
Higher grades (M25, M30) use more cement. Ratio is cement : sand : aggregate.
Results
Sand and aggregate are in cubic feet (cft) — how they’re usually ordered on Indian sites. Cement bags are rounded up to whole bags.
M20 (1:1.5:3)
Cement : sand : aggregate
1 : 1.5 : 3
Materials to order
50 kg cement bags
8bags (rounded up)
Sand
13.35cft
Aggregate (coarse)
26.70cft
Volume breakdown
Wet volume
0.90m³
Dry volume (× 1.54 for voids & wastage)
1.386m³
How this is calculated
Formula
- wet_volume = length × width × depth (or enter volume directly)
- Convert ft → m or cft → m³ if imperial is selected
- dry_volume = wet_volume × 1.54
- Split dry volume by cement : sand : aggregate ratio for selected grade
- Cement → 50 kg bags, rounded up
- Sand & aggregate → cubic feet (× 35.3147)
Assumptions
- Wet volume = length × width × depth, or enter total volume directly.
- Dry volume adds 54% (× 1.54) for voids between particles and site wastage.
- Uses Indian nominal mix ratios for M10–M30.
- Cement sold in 50 kg bags; density ≈ 1440 kg/m³.
- M25 and M30 are often design mixes on site — nominal ratios are approximate.