Work out how much concrete you need. This free concrete / cement calculator finds volume for a slab, footing or column, with premix bags and a 1:2:4 cement-sand-gravel breakdown.
Pour shape
m
m
cm
cm
m
%
Pick the shape and enter the dimensions. Thickness/diameter are in cm (or inches in feet mode). The result includes premixed bags and a 1:2:4 cement-sand-gravel breakdown if mixing your own.
Concrete volume
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Enter your dimensions
Volume (yd³)
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Premix 20 kg bags
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Cement (1:2:4)
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Sand · Gravel
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Volume = the shape’s dimensions, plus a waste allowance. Premix is estimated at about 0.011 m³ per 20 kg bag. The 1:2:4 mix is a common general-purpose ratio (~1 part cement, 2 sand, 4 gravel); check your mix design for structural work.
Use this free concrete calculator to work out how much concrete or cement you need. Enter a slab, footing or column and get the volume, bags and a cement-sand-gravel mix.
What this concrete / cement calculator does
A concrete and cement calculator finds the volume of your pour, then converts it into premixed bags and, if you’re mixing your own, a 1:2:4 cement-sand-gravel breakdown.
A 4 × 3 m slab, 10 cm thick is 1.2 m³ — about 110 premix bags, or a 1:2:4 mix of roughly 384 kg cement, 0.6 m³ sand and 0.96 m³ gravel.
Concrete mix ratios
Mix (C:S:G)
Use
1:2:4
General-purpose (paths, slabs)
1:1.5:3
Stronger structural work
1:3:6
Foundations, mass fill
Bags or mix your own?
For small jobs, premixed bags are simplest — just add water. For larger pours, buying cement, sand and gravel separately and mixing to a ratio is usually cheaper. Always add a waste allowance (about 10%) for spillage and uneven ground.
How to use the concrete calculator
Pick the shape — slab, footing or column.
Enter dimensions, pours and waste %.
Read volume, bags and the mix breakdown.
Concrete / Cement FAQ
How much concrete do I need?
Multiply length × width × thickness for a slab. A 4 × 3 m slab at 10 cm thick is 1.2 m³ — about 110 premixed 20 kg bags.
How many bags of concrete per cubic metre?
Roughly 90 bags of 20 kg premix per cubic metre (about 0.011 m³ each). Always check the yield printed on your bag.
What is a 1:2:4 concrete mix?
One part cement, two parts sand, four parts gravel by volume — a common general-purpose ratio for paths and slabs.
How do I calculate concrete for a column?
Use π × radius² × height. A 30 cm diameter column 3 m tall is about 0.21 m³ of concrete.
Should I add extra for waste?
Yes — around 10% covers spillage, uneven ground and over-excavation. The calculator includes an adjustable waste allowance.
Is the concrete calculator free?
Yes, this concrete / cement calculator is completely free, needs no sign-up, and gives instant results in your browser.
