Our Cement Quantity Calculator tells you exactly how many bags of cement, how much sand, and how much aggregate (gravel) you need for any concrete slab, foundation, or column. Just enter dimensions and your mix ratio.
Cement Quantity Calculator
How to Calculate Cement Quantity
The standard formula accounts for the fact that dry concrete mix bulks up by about 54% when mixed with water:
- Wet Volume = Length × Width × Thickness
- Dry Volume = Wet Volume × 1.54 (dry bulking factor)
- Volume of Cement = (Cement Ratio / Total Ratio) × Dry Volume
- Weight of Cement = Volume × 1440 kg/m³ (bulk density of cement)
- Bags = Weight ÷ Bag size (50 kg or 25 kg)
Concrete Mix Ratios (Cement:Sand:Aggregate)
| Mix | Grade | Use |
|---|---|---|
| 1:2:4 | M15 | Non-structural: pathways, garden floors |
| 1:1.5:3 | M20 | Most RCC slabs, beams, columns |
| 1:1:2 | M25 | Heavy-duty: bridges, industrial floors |
Tips for Accurate Cement Estimation
- Always add 5–10% extra for wastage and spillage
- Use OPC 53 grade cement for structural work (slabs, columns, beams)
- For plastering (12mm thick), the ratio is usually 1:4 (cement:sand)
- Store cement in a dry place — it loses strength rapidly when exposed to moisture
- Buy cement in batches — don’t let it sit more than 3 months
Cement Quantity for Common Projects (M20 mix)
| Project | Approx. Bags (50kg) |
|---|---|
| 10×10 ft slab, 4 inch thick | 7–8 bags |
| 20×20 ft slab, 5 inch thick | 28–30 bags |
| Column 9″×9″×10 ft height | 4–5 bags |
| 1000 sq ft house roof slab | 70–80 bags |
FAQs
How many bags of cement per cubic metre of concrete?
For M20 mix (1:1.5:3), approximately 8–9 bags (50kg) per cubic metre of finished concrete.
What is the density of cement?
The bulk density of ordinary Portland cement (OPC) is 1440 kg/m³.
How much sand per bag of cement?
For M20 mix, roughly 2 cubic feet of sand per 50kg bag of cement.
Why do we multiply by 1.54 when calculating cement quantity?
Dry concrete materials (cement, sand, aggregate) bulk up by about 54% compared to wet, compacted concrete volume. Multiplying wet volume by 1.54 gives the dry volume needed to order materials.