Concrete Slab Calculator
Concrete for patios, garage & shed floor slabs
Planning a patio, garage, shed or driveway slab? Enter the slab dimensions and thickness to get the concrete you need in cubic yards and in bags.
How thick should a slab be?
4 inches suits patios, walkways and shed floors. Use 5–6 inches for driveways or anything carrying vehicle weight. Always pour over a compacted gravel base.
Ordering tips
Slabs are almost always cheaper as ready-mix once you pass roughly half a cubic yard. Add 10% so you're never caught short mid-pour.
Base, gravel and rebar
A slab is only as good as what's under it. Pour over 4–6 inches of compacted gravel for drainage and a stable, frost-resistant base, and add wire mesh or rebar for slabs that carry vehicles. Pour on a dry day above 50°F, then keep the surface damp for several days so it cures slowly and reaches full strength.
Concrete Slab Calculator: frequently asked questions
How much concrete for a 10x10 slab?
A 10×10 ft slab at 4 inches thick needs about 1.23 cubic yards (with 10% waste, ~1.36 yd³).
How thick should a patio slab be?
4 inches is standard for a residential patio over a compacted base.
Do I need gravel under a concrete slab?
Yes — 4–6 inches of compacted gravel gives drainage and a stable base that resists cracking and frost heave. Pouring directly on bare soil is the most common cause of a failed slab.