Concrete Details
Material Required
Material Breakdown
Dry volume basis| Material | Volume (m³) | Quantity | Weight (kg) | Est. Cost |
|---|
How Concrete Quantity is Calculated
Concrete work in India is almost always estimated using a nominal mix — a fixed ratio of cement, sand (fine aggregate) and coarse aggregate by volume, set out in IS 456. The steps below are exactly what this calculator automates.
Step 1: Find the wet volume
Wet Volume = Length × Width × Thickness
This is the actual volume of concrete you need once it's poured and compacted — for example, a 3m × 3m slab at 100mm thickness is 3 × 3 × 0.1 = 0.9 m³.
Step 2: Convert to dry volume
Dry Volume = Wet Volume × 1.54
Loose, dry cement, sand and aggregate have air gaps between particles. Once mixed with water and compacted, that volume reduces by roughly 30-35% — so you need about 1.54 times more dry material than the final wet volume you're trying to achieve.
Step 3: Split by mix ratio
For a mix ratio of a:b:c (cement:sand:aggregate), each material's volume is the dry volume multiplied by its share of the total parts (a+b+c):
| Grade | Ratio (cement:sand:aggregate) | Typical use |
|---|---|---|
| M10 | 1:3:6 | PCC, leveling course, non-structural fill |
| M15 | 1:2:4 | PCC, flooring base, footings in light soil |
| M20 | 1:1.5:3 | RCC slabs, beams and columns — most common residential grade |
| M25 | 1:1:2 | Heavier structural loads, water-retaining structures |
Step 4: Convert to bags and buyable units
- Cement: one 50kg bag occupies about 0.0347 m³, so bags needed = cement volume ÷ 0.0347.
- Sand & aggregate: usually bought by the cubic foot (cft) or tonne. 1 m³ = 35.31 cft; sand is estimated at ~1,600 kg/m³ and aggregate at ~1,550 kg/m³.
What this calculator doesn't include
- Reinforcement steel (TMT bars) — that comes from your structural design, not the nominal mix.
- Formwork/shuttering cost and labour charges.
- Water quantity — typically 0.4-0.5 times the cement weight by mass (water-cement ratio), but this varies by site conditions and admixtures.
For example, a 3m × 3m slab at 100mm thickness in M20 grade works out to a wet volume of 0.9 m³, a dry volume of about 1.46 m³ (with 5% wastage), 8 bags of cement, about 14 cft of sand and 28 cft of aggregate. Enter these same figures into the calculator above to reproduce this result.