Concrete mix calculation for M20 (cement, sand & aggregate per m³)
M20 is one of the most common grades for residential RCC work. Its nominal mix is 1 : 1.5 : 3 (cement : sand : coarse aggregate). This guide shows how to find the material quantity for one cubic metre of wet, compacted M20 concrete.
Step 1 — Dry volume
Wet concrete is denser than its loose ingredients, so we multiply the wet volume by a dry-volume factor of 1.54:
Dry volume for 1 m³ = 1 × 1.54 = 1.54 m³
Step 2 — Split by mix ratio
Sum of ratio parts = 1 + 1.5 + 3 = 5.5.
- Cement = (1 / 5.5) × 1.54 = 0.28 m³ ÷ 0.0347 m³/bag ≈ 8.07 bags (≈ 403 kg)
- Sand = (1.5 / 5.5) × 1.54 ≈ 0.42 m³
- Coarse aggregate = (3 / 5.5) × 1.54 ≈ 0.84 m³
Summary — per 1 m³ of M20 concrete
| Material | Approx. quantity |
|---|---|
| Cement | 8.07 bags (≈ 403 kg) |
| Sand (fine aggregate) | 0.42 m³ |
| Coarse aggregate (20 mm) | 0.84 m³ |
| Water (w/c ≈ 0.5) | ≈ 200 litres |
Common nominal mixes
| Grade | Nominal mix (C:S:A) | Cement (bags/m³) |
|---|---|---|
| M7.5 | 1:4:8 | ≈ 3.4 |
| M10 | 1:3:6 | ≈ 4.4 |
| M15 | 1:2:4 | ≈ 6.3 |
| M20 | 1:1.5:3 | ≈ 8.1 |
| M25 | 1:1:2 | ≈ 11.1 |
Nominal mixes are for estimation and small works. For structural RCC, the grade, mix design, water-cement ratio and reinforcement must be designed and stamped by a licensed structural engineer as per IS 456.
In CivilOS you pick the grade and volume, choose PCC or RCC, and it returns cement bags, sand, aggregate and steel with the working shown — ready to drop into your BOQ and estimate.
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