Concrete volume and mix

Work out concrete volume for a slab, footing or column, then the cement bags, sand and stone for your mix. Metric, 50 kg bags, waste allowance included.

✓ Free, no sign-up ✓ Works on your phone, standing at the problem ✓ The formula and the assumptions are always shown

IT CIVILS  ·  IT ADMIN BUSTER
1 Enter the job

Concrete volume and mix

Worked out at itcivils.com/free/calculators/  ·  Free construction calculators for site teams.
Check every quantity against your own specification and your supplier's own figures before ordering.

A worked example

This is the job the page opens with, already worked out. Change any figure above and the answer changes with it.

The job

What are you pouring
Slab or surface bed
Length
10 m
Width
5 m
Thickness
100 mm
How many
1
Waste and over-order
10 %
Mix by volume
1:2:4, slabs and general work, about 25 MPa

The answer

5.5m³  ·  Concrete to order or batch

Each element
5 m³
Net volume, 1 no
5 m³
Waste at 10%
0.5 m³
Cement, 50 kg bags
34.87 bags
Cement by mass
1 744 kg
Sand
2.42 m³
Sand, wheelbarrows
37.23
Stone
4.84 m³
Stone, wheelbarrows
74.46
Water, roughly
958.9 litres

The working

10 m × 5 m × 100 mm × 1 = 5 m³, plus 10% = 5.5 m³.
Wet volume × 1.54 gives the dry loose volume, then split by 1:2:4.

What it assumes

All eighteen calculators

Every one has its own page, so you can bookmark the one you use most.

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On the job

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Get the next tool when it lands

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Why these are free, and what they assume

These come from ten years on site: first in contracting on production and civil works, then in consulting doing construction monitoring for consultants appointed by the City of Cape Town. Working a quantity out twice, because the first answer was on a piece of board that blew away, is a thing that happens to everybody.

Every calculator shows the formula it used and the assumptions it made, because a number with no working behind it is worth nothing on site. Where a figure varies by material or supplier, it is an input you can change rather than something hidden. Check the answers against your own specification and your supplier's own figures before you order. These help you work faster, they do not replace your own judgement.

If they save you time, the paid IT Admin Buster packs cover the admin side: progress report templates, daily diaries, inspection checklists and the wording banks that go with them.