Concrete Mix Calculator (Cement, Sand, Aggregate)
By Santaji GadepatilinUpdated October 27, 2026
A concrete mix ratio such as 1:1.5:3 sets how much cement, sand and aggregate go into each batch. Converting wet volume into dry material quantities is the key step in ordering.
How to use the concrete mix calculator
Enter the wet volume and choose the mix. The dry volume, cement bags, sand and coarse aggregate are calculated.
This calculator assumes the sand-to-aggregate ratio is 1 : 2, as in all the listed nominal mixes.
Example — 1 m³ of M20 (1 : 1.5 : 3)
- Dry volume = 1.54 m³
- Cement = 1.54 ÷ 5.5 = 0.28 m³ = 8.1 bags
- Sand = 0.28 × 1.5 = 0.42 m³
- Aggregate = 0.28 × 3 = 0.84 m³
Nominal mixes follow common Indian practice (IS 456). For structural work, always follow your structural engineer’s design.
Nominal mix ratios by grade
| Grade | Mix (cement : sand : aggregate) | Typical use |
|---|---|---|
| M10 | 1 : 3 : 6 | Levelling course, PCC |
| M15 | 1 : 2 : 4 | Floors, pathways |
| M20 | 1 : 1.5 : 3 | RCC slabs, beams, columns (small buildings) |
| M25 | 1 : 1 : 2 | Heavier RCC work |
The number after M is the characteristic compressive strength in N/mm² at 28 days. Above M20, design mixes based on lab tests are recommended.
Materials for 1 m³ by grade
| Grade | Cement bags (50 kg) | Sand (m³) | Aggregate (m³) |
|---|---|---|---|
| M10 | 4.4 | 0.462 | 0.924 |
| M15 | 6.3 | 0.440 | 0.880 |
| M20 | 8.1 | 0.420 | 0.840 |
| M25 | 11.1 | 0.385 | 0.770 |
Values use the 1.54 dry-volume factor and a cement density of 1,440 kg/m³. Add 2–5% for wastage.
Water–cement ratio
Strength depends heavily on the water–cement ratio. Typical values are 0.45–0.55 for structural concrete. Adding extra water to make concrete easier to place reduces strength and durability. Use a plasticiser instead.
Curing
Concrete gains about 70% of its 28-day strength in 7 days if kept moist. Cure by ponding, wet hessian or curing compound for at least 7 days (10–14 days in hot, dry weather).
Frequently asked questions
What is the M20 mix ratio?
For nominal mixes, M20 is 1 : 1.5 : 3 (cement : sand : aggregate). Design mixes for important structures are proportioned by a lab.
Why multiply by 1.54?
To allow for voids and shrinkage — dry ingredients occupy about 54% more volume than the finished concrete.
How much water is needed?
Typically a water–cement ratio of about 0.45–0.55 by weight for these mixes. Too much water weakens concrete.
How many cement bags are needed for 1 m³ of M20 concrete?
About 8 bags of 50 kg for a nominal 1 : 1.5 : 3 mix.
Why multiply by 1.54?
Dry materials shrink when water is added and voids fill, so about 1.54 m³ of dry materials make 1 m³ of wet concrete.