Concrete Calculator
Cement bags, sand and aggregate for a slab, column or footing in M5 to M25 nominal mixes.
About Concrete Calculator
This concrete calculator works out how much cement, sand and aggregate you need for an RCC slab, column or footing. Pick the element, enter its dimensions in feet or metres and how many you are casting, choose the concrete grade from M5 to M25 and add a wastage allowance.
The result shows cement in 50 kg bags and sand and aggregate in cubic metres, cubic feet and brass, the units used by suppliers across India. It is useful for homeowners, site engineers and contractors estimating material for a slab before ordering. The calculator uses nominal mix ratios, is free and runs in your browser.
How to use Concrete Calculator
- Pick the element — slab, column or footing — and the unit.
- Enter the dimensions and how many of them you are casting.
- Choose the concrete grade and a wastage allowance.
- Read cement bags, sand and aggregate in m³, cft and brass.
Frequently asked questions
Why multiply by 1.54?
Wet concrete is about 35–54% smaller in volume than the dry ingredients because sand fills voids between aggregate and cement fills voids in sand. The standard site factor for dry volume is 1.54.
How many bags of cement are in 1 m³ of M20?
For nominal M20 (1:1.5:3): 1.54 ÷ 5.5 × 1440 ÷ 50 ≈ 8.06 bags per m³ of concrete.
Should I use nominal mix for M25 and above?
IS 456 recommends design mix for M25 and higher grades. Nominal ratios here are for estimation only — follow your structural engineer’s mix design.
What is a brass?
A brass is 100 cubic feet — the unit in which sand and aggregate are usually sold in many parts of India.
How do I calculate concrete for a slab?
Multiply length × width × thickness to get the wet volume, multiply by 1.54 for dry volume, then split it by the mix ratio. The calculator does all of this and adds wastage.
What is the mix ratio of M20 concrete?
M20 nominal mix is 1 : 1.5 : 3 of cement, sand and aggregate.
How much cement is needed for a 1000 sq ft slab?
For a 5-inch M20 slab, it is roughly 100–110 bags depending on wastage. Enter your exact size to get a precise figure.
People also search for
concrete calculator · concrete calculator india · concrete calculator formula · concrete calculator m20 · concrete calculator m25 · concrete calculator online · concrete calculator for slab · concrete calculator cement sand aggregate · concrete calculator m3 · concrete calculator online free · how to concrete calculator · concrete calculator square feet