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Concrete Calculator: Volume, Cement, Sand and Aggregate

This free concrete calculator finds the volume of concrete for a slab, footing or path, then estimates the cement bags, sand and aggregate for the mix ratio you choose. It adds an allowance for waste.

By Debmedia Technologies LLP · Kolkata, India · Updated

What Is It and When Do You Need It?

Concrete is ordered by volume, and mixed by ratio. Ordering too little means a cold joint, and too much wastes money. For small jobs mixed on site, the cement, sand and aggregate are bought by bag and cubic metre.

Enter the size of the slab and the mix, and the tool gives the volume of concrete and the materials.

How to Use This Tool

  1. Enter length, width and thickness.
  2. Choose the mix ratio.
  3. Enter a waste allowance.
  4. Press Calculate.

How the Calculation Works

Wet volume = length × width × thickness × (1 + waste). Dry volume = wet volume × 1.54. With a mix of 1 : s : a, the parts total 1 + s + a. Cement volume = dry volume ÷ parts, in cubic metres, and each 50 kg bag is 0.0347 m³. Sand = s × cement volume parts, and aggregate = a × parts.

Worked Example

A slab 5 m × 4 m × 10 cm needs 2.0 m³, or 2.1 m³ with 5% waste. For a 1:2:4 mix, that needs about 0.462 m³ of cement (14 bags of 50 kg), 0.924 m³ of sand and 1.848 m³ of aggregate.

Common Uses

  • Slabs, paths and patios.
  • Footings and foundations.
  • Planning a delivery.
  • Costing a job.

Tips and Common Mistakes

  • Order a little extra.
  • Use ready-mix for jobs above about 1 m³.
  • Check local standards for mix strength.

Next, you may need the area calculator, volume calculator, paint calculator, tile calculator.

Everything runs in your browser. Nothing you type is uploaded, stored or sent to any outside service.

Frequently Asked Questions

Multiply length × width × thickness, all in metres. A slab 5 m × 4 m × 0.10 m needs 2 cubic metres.
The wet volume is increased by about 54 percent to get the dry volume of materials, then shared in the mix ratio. A 50 kg bag of cement is about 0.0347 cubic metres.
Spillage, uneven ground and over-excavation use extra concrete. Five to ten percent is common.
No. It is an estimate for quantities. Structural work needs a design by an engineer.

Disclaimer: results are calculated in your browser from the numbers you enter. Check important results before you rely on them for money, health, safety or legal decisions.