BuildCalc

Concrete Patio Calculator

Estimate a concrete patio from the slab down. Enter the patio size and thickness and the calculator returns the cubic yards, the bag count, an estimated ready-mix cost and — the part most calculators leave out — the compacted gravel base that goes underneath.

Concrete for the patio
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    How it works

    Slab volume (cu ft) = length × width × (thickness ÷ 12); cubic yards = cu ft ÷ 27. The gravel base uses the same area at your chosen base depth, and its weight assumes about 1.4 US tons per cubic yard of compacted gravel. Ready-mix cost = cubic yards including waste × your price per cubic yard.

    Frequently asked questions

    How thick should a concrete patio be?

    Four inches is standard for a patio that carries foot traffic and furniture. Go to 5–6 inches if a vehicle, hot tub or heavy structure will sit on it, and thicken the edges where the slab is unsupported.

    How much concrete for a 12x16 patio?

    A 12 × 16 ft patio at 4 inches is 64 cubic feet, or about 2.37 cubic yards before waste — call it 2.6 cubic yards ordered. That is a ready-mix job; in bags it would be about 118 bags of 80 lb.

    Do I need gravel under a concrete patio?

    Yes in almost all cases. Four to six inches of compacted gravel gives drainage and a stable, uniform bearing surface, which is what stops differential settlement and cracking. The calculator sizes it along with the slab.

    What does a concrete patio cost?

    The concrete itself follows cubic yards × your local ready-mix price, commonly $140–$180 per yard. A finished patio costs considerably more once forming, base, labour, finishing and control joints are added — this figure is the material.

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    Estimates are for planning only. Material yields, densities and code requirements vary — confirm quantities with your supplier and local building code before ordering.