How many cement bags do you need for 1 cubic metre of M15, M20 or M25 concrete? This guide shows the standard dry volume method step by step, gives a ready table for every nominal mix from M5 to M25, adds sand, aggregate and water quantities, and includes a free calculator for any volume.
| M10 (1:3:6) | 4.4 bags (222 kg) |
|---|---|
| M15 (1:2:4) | 6.3 bags (317 kg) |
| M20 (1:1.5:3) | 8.1 bags (403 kg) |
| M25 (1:1:2) | 11.1 bags (554 kg) nominal; about 7–8 bags with a design mix |
Cement, sand and aggregate for 1 m³ of concrete (all grades)
| Grade | Nominal mix | Cement (kg) | Cement (bags) | Sand (m³) | Aggregate (m³) |
|---|---|---|---|---|---|
| M5 | 1:5:10 | 139 | 2.8 | 0.48 | 0.96 |
| M7.5 | 1:4:8 | 171 | 3.4 | 0.47 | 0.95 |
| M10 | 1:3:6 | 222 | 4.4 | 0.46 | 0.92 |
| M15 | 1:2:4 | 317 | 6.3 | 0.44 | 0.88 |
| M20 | 1:1.5:3 | 403 | 8.1 | 0.42 | 0.84 |
| M25 | 1:1:2 | 554 | 11.1 | 0.39 | 0.77 |
Step-by-step calculation for M20
Wet concrete has fewer voids than the loose dry materials that go into it, so the dry volume is larger than the finished volume. The usual site factor is 1.54 (some textbooks use 1.52 to 1.57).
- Dry volume = 1 m³ × 1.54 = 1.54 m³
- Sum of ratio for 1:1.5:3 = 1 + 1.5 + 3 = 5.5
- Cement volume = 1.54 × 1 ÷ 5.5 = 0.28 m³
- Cement weight = 0.28 × 1,440 = 403.2 kg → 403.2 ÷ 50 = 8.06 bags
- Sand = 1.54 × 1.5 ÷ 5.5 = 0.42 m³ (14.8 cft)
- Aggregate = 1.54 × 3 ÷ 5.5 = 0.84 m³ (29.7 cft)
- Water at a water-cement ratio of 0.50 = 403 × 0.50 ≈ 202 litres
One 50 kg bag of cement has a loose volume of about 0.0347 m³ (1.23 cft), which is why site gauge boxes are often made 35 litres. Keep the water-cement ratio in check with our water-cement ratio guide.
Free cement, sand & aggregate calculator
Why M25 should not be made as 1:1:2
IS 456:2000 (cl. 9.1.1 and Table 9) allows nominal mixes only for M20 and lower grades. For M25 and above, a design mix to IS 10262:2019 is required. A design mix uses graded aggregates, the correct water content and usually a plasticiser, so an M25 mix commonly needs only about 340–400 kg of cement per m³ (about 7–8 bags), not the 554 kg that a 1:1:2 ratio gives. Too much cement increases cost, heat and shrinkage cracking. Try our free concrete mix design calculator.
IS 456 cement content limits
| Exposure (RCC) | Minimum cement (kg/m³) | Maximum w/c ratio | Minimum grade |
|---|---|---|---|
| Mild | 300 | 0.55 | M20 |
| Moderate | 300 | 0.50 | M25 |
| Severe | 320 | 0.45 | M30 |
| Very severe | 340 | 0.45 | M35 |
| Extreme | 360 | 0.40 | M40 |
Quick site examples
| Work | Volume | M20 cement |
|---|---|---|
| Slab 4 × 3 m, 125 mm thick | 1.5 m³ | 12.1 bags |
| Column 300 × 300 mm, 3 m high | 0.27 m³ | 2.2 bags |
| Beam 230 × 380 mm, 4 m long | 0.35 m³ | 2.8 bags |
| Footing 1.5 × 1.5 × 0.4 m | 0.90 m³ | 7.3 bags |
Frequently asked questions
How many bags of cement are in 1 cubic metre of M20 concrete?
About 8 bags (403 kg) for a nominal 1:1.5:3 mix using the dry volume factor of 1.54.
How many bags of cement are needed for 1 m³ of M15?
About 6.3 bags (317 kg) for a 1:2:4 mix.
Why is 1.54 used in concrete calculation?
Dry cement, sand and aggregate contain air voids and bulk up. When water is added they compact, so about 1.54 m³ of dry materials make 1 m³ of wet concrete.
How many cubic feet are in 1 bag of cement?
About 1.23 cft (0.0347 m³) for a 50 kg bag at a bulk density of 1,440 kg/m³.
Related guides
- Concrete Mix Design Calculator (IS 10262:2019)
- House Construction Cost in India 2026
- Bricks, Cement & Sand for Brickwork
- Plaster Calculator
References: IS 456:2000 (cl. 8.2.4, 9.1.1, Tables 5 and 9) and IS 10262:2019.
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