Utility
Concrete Volume & Material Calculator
Work out how much concrete a slab, beam, column or footing needs, and what goes into it — cement in bags, sand and aggregate in both cubic metres and cubic feet. Nominal mixes to IS 456, which stops at M20 and says so.
What you are pouring
Grade
Nominal mix 1 : 1.5 : 3 — cement : sand : aggregate, by volume.
The assumptions
- Loose cement, sand and aggregate occupy far more than the concrete they make, because the sand fills the voids between the stones and the cement fills the voids between the sand. 1.54 is the figure in widest use; 1.52 and 1.55 are both published and both defensible. It multiplies straight through every quantity below, so it is here rather than hidden.
- Spillage, over-excavation and what stays in the mixer. Three to five per cent is usual for a controlled pour, more for foundations on uneven ground.
- By weight, and typically 0.4 to 0.6. Lower gives stronger concrete and a harsher mix to place. IS 456 caps it by exposure condition, and that limit is not reproduced here — check the standard for the exposure you are building in.
What to order
- Concrete placed
- 3 m³
- Order this much
- 3.15 m³
- Dry volume of materials
- 4.851 m³
- Weight of concrete
- 7.56 t
Cement
26 bags
1270 kg
- Sand
- 1.32 m³ · 47 cft
- Coarse aggregate
- 2.65 m³ · 93 cft
- Water
- 635 L
How to use it
- Choose what you are pouring and enter its dimensions in metres. Set how many identical elements there are.
- Pick the grade. M5 to M20 have nominal mixes in IS 456; above that the tool gives volume and weight only.
- Adjust the dry factor, wastage and water/cement ratio if your practice differs from the defaults shown.
- Order the volume marked "order this much" — it includes the wastage allowance.
- Take the cement bags, and the sand and aggregate in cft, to the merchant.
How it works
Volume is length × width × thickness for a slab, beam, column or footing, and π/4 × d² × height for a circular column.
That wet volume is multiplied by the dry factor to get the loose material needed, then split in the mix ratio.
Cement volume becomes weight at 1440 kg/m³, and weight becomes bags at 50 kg each, rounded up.
Water follows the cement weight and the water/cement ratio. A litre of water weighs a kilogram, so no further conversion is involved.
The mix ratios are the same ones on the concrete grades reference page — one table, read by both, so they cannot disagree.
Common questions
Why is the dry volume larger than the concrete?
Because loose materials are mostly air. Aggregate has gaps between the stones, sand fills those gaps, and cement fills the gaps between the sand — so a cubic metre of finished concrete needs about one and a half cubic metres of dry material to make it. The multiplier is a rule of thumb rather than a measurement, which is why it is an input you can change rather than a constant.
Why is there no mix for M25?
Because IS 456 does not give one. Nominal mixes stop at M20; above that the standard requires a design mix, proportioned by weight against a target strength and the materials actually being used. "M25 = 1:1:2" is printed on plenty of sites and is not in the standard. The calculator gives you the volume and the weight for those grades and stops short of inventing proportions.
Why cubic feet as well as cubic metres?
Because that is how sand and aggregate are sold across India. A tipper is quoted in cft, or in units of a hundred of them, so a figure only in cubic metres has to be converted before anyone can buy anything. Both are shown so the number you take to the merchant is the number on the screen.
Do the bags round up?
Yes. A merchant does not split a bag, so the figure shown is whole bags that cover the cement needed, with the exact weight in kilograms underneath it.
Does this account for reinforcement?
No. The volume is the gross volume of the element; steel displaces roughly one to two per cent of it in normal reinforced work, which is well inside the wastage allowance and in the direction of ordering slightly too much. For the steel itself, the rebar weight chart gives mass per metre by diameter.
Rebar weight chart →