Concrete material calculator — cement, sand and aggregate
Calculate your concrete materials
Enter dimensions or a direct volume, pick a grade — results update as you type.
Materials required
Dry volume: 0
- Cement (bags)0
- Cement (weight)0
- Sand (volume)0
- Sand (weight)0
- Aggregate (volume)0
- Aggregate (weight)0
- Water0
- Estimated material cost₹0
Sample figures shown for illustration — pending verification against real Tirupati market rates before publishing as fact.
Concrete grades and nominal mix ratios
"Nominal mix" ratios are the nationally standard cement : sand : aggregate proportions used for small residential work in India, where a design mix (lab-tested for a specific strength) usually isn't required. M20 is the grade most commonly used for house slabs, beams and columns; M25 and above are used where a structural engineer's drawing specifically calls for higher strength.
| Grade | Ratio (cement : sand : aggregate) |
|---|---|
| M5 | 1 : 5 : 10 |
| M7.5 | 1 : 4 : 8 |
| M10 | 1 : 3 : 6 |
| M15 | 1 : 2 : 4 |
| M20 | 1 : 1.5 : 3 |
| M25 | 1 : 1 : 2 |
How this is calculated
Concrete is measured wet (as it's poured) but bought dry (as bagged cement, loose sand and aggregate) — dry ingredients take up more space than the compacted wet mix because of air gaps between particles. The standard correction is the dry volume factor of 1.54: multiply the wet (poured) volume by 1.54 to get the dry volume of materials you actually need to buy.
That dry volume is then split across cement, sand and aggregate in the ratio for the chosen grade. Cement is converted from volume to weight using its bulk density of 1440 kg per cubic metre, then divided by 50 to get standard bags. Sand and aggregate are converted to cubic feet (× 35.3147, the number of cubic feet in a cubic metre) because that's how local suppliers quote them, and to tonnes using typical bulk densities of 1.55 t/m³ for sand and 1.5 t/m³ for aggregate.
Worked example: one cubic metre of M20
For 1 cubic metre of wet M20 concrete (ratio 1 : 1.5 : 3, 5.5 parts total):
Dry volume = 1 × 1.54 = 1.54 m³ Cement volume = (1 ÷ 5.5) × 1.54 = 0.28 m³ → 0.28 × 1440 = 403.2 kg → 403.2 ÷ 50 = 8.06 bags Sand volume = (1.5 ÷ 5.5) × 1.54 = 0.42 m³ → 0.42 × 35.3147 = 14.8 cft (0.65 tonnes) Aggregate volume = (3 ÷ 5.5) × 1.54 = 0.84 m³ → 0.84 × 35.3147 = 29.7 cft (1.26 tonnes)
How much concrete for a slab
For a 1,000 sq ft slab at a typical 4-inch (0.1016 m) thickness, the wet volume works out to about 9.44 cubic metres. At M20, that's roughly 76 cement bags, 140 cft of sand and 280 cft of aggregate — before any wastage allowance. Always confirm slab thickness and grade against your structural engineer's drawing rather than a thumb rule; this calculator gives you the material quantities once you know those two numbers.
Frequently asked questions
How many cement bags for 1000 sqft slab?
For a 1,000 sq ft slab at 4 inches thick in M20 concrete, you need approximately 76 cement bags — see the worked example above for the full calculation. The exact figure depends on your actual slab thickness and grade, so confirm both against the structural drawing first.
How many bags of cement are there in 1 cubic metre of M20 concrete?
About 8.06 bags (403 kg) of cement, plus 14.8 cft of sand and 29.7 cft of aggregate, for 1 cubic metre of wet M20 concrete.
Why is the dry volume multiplied by 1.54?
Because dry, loose materials (cement, sand, aggregate) take up about 54% more space than the same materials once mixed, wetted and compacted into place. The 1.54 factor is standard across Indian construction practice.
Which concrete grade should I use for a house slab?
M20 is the standard grade for residential slabs, beams and columns in most independent houses. Higher grades (M25+) are used only where a structural engineer specifies them for higher load-bearing requirements.
What's the difference between nominal mix and design mix?
A nominal mix (like the M5–M25 ratios here) uses fixed, standard proportions and is allowed for small, non-critical residential work. A design mix is lab-tested for a specific target strength using the actual local cement, sand and aggregate, and is required for larger or structurally critical work.
How much water do I need per bag of cement?
A water–cement ratio of 0.5 is standard, meaning roughly half a bag's weight in water (about 25 litres per 50 kg bag). Too much water weakens the concrete; too little makes it unworkable — 0.4 to 0.6 is the usual adjustable range.
Building on your own land?
Building vs. buying — the real comparison
This calculator is for people building on land they already own. If you're still deciding between building yourself and buying a finished flat, this comparison covers the real costs and timelines of both.