Volume of concrete needed for a slab or footing.
Free to use, no sign-up required. Concrete Estimator is one of 198 tools built into Xenition, alongside a chat that can use them for you.
Gives the volume of concrete for a rectangular slab, pad or footing, and roughly how many 25 kg bags of pre-mixed concrete that is.
Volume = length × width × (depth ÷ 100), in cubic metres. Bags = volume ÷ 0.017, rounded up, which assumes one 25 kg bag of dry mix yields about 0.017 m³ of concrete.
A 5 m × 4 m slab 10 cm deep is 5 × 4 × 0.1 = 2 m³. At 0.017 m³ per bag that is 117.6, so about 118 bags of 25 kg.
Bags suit small jobs such as post holes or a shed base under a cubic metre. At 2 m³ you would be mixing over a hundred bags by hand, which is the point where most people order a truck.
Yes. The tool gives the exact geometric volume with no margin. Uneven ground, a sub-base that dips and spillage mean ordering around 5 to 10% more is common practice.
You do not have to open Concrete Estimator to use it. Ask Xenition in plain language and it runs the right tool, then carries the answer into whatever you are working on — a document, a spreadsheet, a deck.