Concrete calculator
Example: 5 × 4 × 0.25 m = 5 m³ of M20 with 2% wastage → about 2,056 kg cement (41.1 bags), 2.14 m³ sand and 4.28 m³ aggregate. 1 m³ = 35.31 cft; 1 brass = 100 cft.
How many cement bags are in 1 m³ of concrete?
For an M20 nominal mix (1:1.5:3), 1 m³ of concrete needs about 8.06 bags (403 kg) of cement, 0.42 m³ of sand and 0.84 m³ of aggregate. That uses a dry volume factor of 1.54, cement density of 1,440 kg/m³ and 50 kg bags. M15 (1:2:4) needs about 6.34 bags and M10 (1:3:6) about 4.44 bags.
The formula
Cement (m³) = dry volume × cement part ÷ sum of parts
Cement (kg) = cement m³ × 1,440 · bags = kg ÷ 50
Sand (m³) = dry volume × sand part ÷ sum of parts
Aggregate (m³) = dry volume × aggregate part ÷ sum of parts
The 1.54 factor allows for voids in dry sand and aggregate and for bulking. It is an empirical allowance, not a code value; 1.52–1.57 are also used, which moves M20 between about 7.96 and 8.22 bags per m³.
| Grade | Nominal mix | Cement bags per m³ | Cement kg per m³ |
|---|---|---|---|
| M7.5 | 1:4:8 | 3.41 | 171 |
| M10 | 1:3:6 | 4.44 | 222 |
| M15 | 1:2:4 | 6.34 | 317 |
| M20 | 1:1.5:3 | 8.06 | 403 |
Why M25 and above need a design mix
IS 456 allows nominal mixes only up to M20. For M25 and above, the mix must be designed (IS 10262:2019) from trial mixes. The "1:1:2 for M25" ratio quoted online isn't a code nominal mix, and would use about 11.1 bags per m³, far more cement than a proper design mix usually needs.
Minimum cement and maximum water-cement ratio (IS 456 Table 5)
| Exposure (RCC) | Min cement (kg/m³) | Max w/c ratio | Min 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 |
As reproduced in the NCB reproduction of IS 456 Table 5. Check the current IS 456 with amendments for your work.
From theoretical cement to cement reconciliation
The calculator gives theoretical cement. On site, compare it with cement actually issued for the same work. A big gap means wastage, a wrong mix or cement leaving the site. In True Site Sync, the cement reconciliation report compares theoretical and actual cement by grade and flags variances above 5%. See the material reconciliation statement and preventing material theft.
Frequently asked questions
How many cement bags are needed for 1 m³ of M20 concrete?
About 8.06 bags (403 kg) for an M20 nominal mix of 1:1.5:3, using a dry volume factor of 1.54 and 50 kg bags.
Why multiply by 1.54?
Dry sand and aggregate have voids and bulk, so you need more dry material than the wet concrete volume. 1.54 is the usual site allowance; 1.52–1.57 are also used.
How much sand and aggregate for 1 m³ of M20?
About 0.42 m³ of sand and 0.84 m³ of aggregate, using the 1.54 dry volume factor.
Can M25 be made with a nominal mix?
No. IS 456 permits nominal mixes only up to M20. M25 and above need a design mix under IS 10262:2019.
How many cft are in 1 m³, and what is a brass?
1 m³ is about 35.31 cft. One brass is 100 cft, a unit commonly used for sand and aggregate in parts of India.
What is the maximum water-cement ratio for RCC?
Under IS 456 Table 5, 0.55 for mild exposure, 0.50 for moderate, 0.45 for severe and very severe, and 0.40 for extreme exposure.
1 cube concrete me kitna cement lagta hai?
M20 (1:1.5:3) me lagbhag 8 bag cement prati cubic meter, M15 me lagbhag 6.3 bag, aur M10 me lagbhag 4.4 bag.
Theoretical cement in, reconciliation out
Record concrete pours and cement issues on site, and see theoretical vs actual cement by grade.
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