How Many Cement Bags in 1 Cubic Metre of Concrete? (M10, M15, M20, M25)
The most-asked estimating question on any site. Here are the bag counts for common nominal mixes, the method behind them and the mistakes to avoid.
Using nominal mixes and the dry-volume method (1.54 × wet volume, cement at 1,440 kg/m³), one cubic metre of concrete needs about 4.4 bags of cement for M10 (1:3:6), 6.3 bags for M15 (1:2:4), 8.1 bags for M20 (1:1.5:3) and 11.1 bags for M25 (1:1:2). Add 2–5% for wastage. Higher grades should use a design mix, which often changes the cement content.
The quick table
| Grade | Nominal mix (C:S:A) | Cement (kg) | Cement (bags of 50 kg) | Sand (m³) | Aggregate (m³) |
|---|---|---|---|---|---|
| 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 |
Figures are for 1 m³ of compacted concrete, before wastage. 1 m³ = 35.31 cubic feet.
The method: dry volume
When cement, sand and aggregate are mixed with water, the voids between particles fill up and the total volume shrinks. So the dry volume of ingredients needed is larger than the finished concrete. The standard site factor is 1.54 (some engineers use 1.52 to 1.57).
Steps for M20 (1:1.5:3):
- Wet volume = 1 m³
- Dry volume = 1 × 1.54 = 1.54 m³
- Sum of ratio = 1 + 1.5 + 3 = 5.5
- Cement volume = 1.54 ÷ 5.5 = 0.28 m³
- Cement weight = 0.28 × 1,440 kg/m³ = 403 kg
- Bags = 403 ÷ 50 = 8.06 bags
- Sand = 0.28 × 1.5 = 0.42 m³; Aggregate = 0.28 × 3 = 0.84 m³
Per cubic foot
Divide the per-m³ figures by 35.31. For M20, that is about 0.23 bags of cement per cubic foot of concrete — or roughly one bag for every 4.4 cft.
Water
For nominal mixes, a water-cement ratio of about 0.45–0.55 is typical. For M20 with 403 kg cement at 0.5, that is about 200 litres of water per m³ — but the right amount depends on aggregate moisture and workability. Read water-cement ratio explained.
Nominal mix vs design mix
IS 456 permits nominal mixes only up to M20. For M25 and above, a design mix prepared by a lab using your actual materials is required. A design mix may use 340–450 kg of cement per m³ for M25–M30 depending on materials, admixtures and exposure conditions — often less than the nominal 1:1:2 figure, with better results. See concrete grades M10 to M40.
Worked example: a footing
A footing 1.5 m × 1.5 m × 0.45 m in M20:
- Volume = 1.5 × 1.5 × 0.45 = 1.01 m³
- Cement = 1.01 × 8.06 = 8.2 bags → order 9 bags with wastage
- Sand = 0.42 m³, Aggregate = 0.85 m³
Common mistakes
- Forgetting the dry factor — underestimates materials by about a third.
- Measuring by headpan instead of gauge boxes — volume batching by eye wastes cement.
- No wastage allowance — add 2–5% depending on site control.
- Using wet sand volumes — damp sand bulks up; correct for bulking or batch by weight.
Key takeaways
- M20 nominal mix needs about 8 bags of cement per m³.
- Use the 1.54 dry factor and 1,440 kg/m³ cement density.
- M25 and above should be design mixes.
- Add 2–5% wastage.
Frequently asked questions
How many bags of cement are required for 1 cubic metre of M20 concrete?
About 8 bags (403 kg) using the nominal mix 1:1.5:3 and a dry volume factor of 1.54, before wastage.
How many bags of cement are in 1 cubic metre of M25 concrete?
Around 11 bags for a nominal 1:1:2 mix. However, M25 should be designed as a design mix under IS 456, which often uses less cement.
Why multiply by 1.54 for concrete?
Dry materials have voids that are filled when water is added and the mix is compacted, so about 54% more dry volume is needed to make one unit of finished concrete.
What is the density of cement used in calculations?
Loose bulk density of 1,440 kg/m³ is the standard figure used for estimating, so one 50 kg bag is about 0.0347 m³ (1.23 cft).
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This guide is general information for planning and buying. Quantities, grades and methods for your structure must follow your approved drawings, your engineer’s specification and the applicable Indian Standards.
