Concrete Slab Calculator
Work out the concrete needed for a slab from its length, width and thickness.
Concrete for a flat slab
A concrete slab — a patio, a shed base, a floor — is a simple rectangular pour, so its volume is length times width times thickness. This works out that volume, so you can order or mix the right amount for the slab, in the units your supplier uses.
Enter the slab's dimensions to see the concrete required.
Thickness, and not running short
The thickness matters more than people expect, both for the volume and for the slab's strength — a path can be thinner, but a slab bearing weight, like a shed base or a driveway, needs adequate depth or it cracks. As with any pour, the cardinal rule is not to run short, because concrete sets and a slab poured in one continuous go is far stronger than one finished in two sessions with a cold joint between. So round up and add a small margin.
Concrete Slab Calculator FAQ
How thick should a concrete slab be?
It depends on the load — a path can be thinner, but a slab bearing weight like a shed base or driveway needs adequate depth or it cracks.
Why is running short with concrete a problem?
Because a slab poured in one continuous go is far stronger. Running out leaves a weak cold joint, so order a little extra.
Is anything uploaded?
No. The calculation happens in your browser.