Concrete Slab Cost Calculator
Cubic yards of ready-mix, mesh and placement labour for a poured slab.
Concrete is the one material where running short is catastrophic rather than inconvenient. A truck holds a fixed load, and once it starts pouring you cannot stop and order another few wheelbarrows — a short pour means a cold joint in the middle of the slab, which is a permanent weak line.
The volume itself is simple: area times thickness divided by 27. What catches people is thickness. Going from four inches to five on a driveway adds 25% to the concrete bill, and going to six inches for a slab that carries a vehicle is not optional if you want it to survive a freeze.
How this calculator works
Every field is editable and the result updates as you type — nothing is submitted anywhere, all the maths runs in your browser. That matters for a number you are about to spend money on: you can see exactly which input moved the answer, and by how much.
What this calculation assumes
Assumes a slab on compacted grade with formwork on all sides and a truck able to reach the pour. Excavation, hauling away spoil, gravel base, pump fees and cold-weather additives are excluded.
Treat the result as an order-of-magnitude check rather than a final quantity. Product packaging changes, regional labour rates vary by a factor of two, and no calculator has seen your actual site.
Frequently asked questions
How thick should a slab be?
Four inches for a garden path, patio or shed floor. Five to six inches for anything a vehicle drives on, with a compacted gravel base beneath. Thicker is not automatically better — an under-compacted base will crack a six inch slab just as readily as a four inch one.
Do I need rebar or mesh?
Wire mesh is adequate for a residential patio or shed base and it holds cracks together rather than preventing them. Rebar matters on driveways, slabs over fill, and anything cantilevered. Either way, control joints cut at regular intervals are what actually decide whether you get visible cracks.
Why is there a 5% overage?
Because a slab is never perfectly formed, and the subgrade always absorbs some mix. Five percent on a cubic yard order is the difference between finishing level and scrambling for a wheelbarrow of bagged concrete. On anything under a yard, order bags instead and mix to the calculated volume.
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