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Concrete Slab Calculator
Sized for a slab specifically, so it costs out the whole assembly — the concrete itself, the reinforcement grid, and the compacted base that goes under it.
Your numbers
Result
Concrete to order
7.82
cubic yards
- Exact volume
- 7.11cubic yards
- 80 lb bags, if mixing
- 353bags
- Rebar needed
- 816linear ft
- 20 ft rebar sticks
- 41sticks
- Gravel base
- 7.11cubic yards
- Base in tons
- 9.96tons
- Slab area
- 576sq ft
How this is calculated
- Concrete volume = length × width × (thickness ÷ 12), then ÷ 27 for cubic yards.
- Rebar grid = bars each way at your spacing, so total linear feet = (bars across × length) + (bars along × width).
- Gravel base = area × (base depth ÷ 12) ÷ 27, at roughly 1.4 tons per cubic yard compacted.
- An 80 lb bag yields about 0.60 cubic feet.
Before you order
- Rebar does nothing lying on the ground. It has to sit in the middle third of the slab on chairs — a grid dragged up 'as you pour' generally is not where you think it is.
- Control joints go in at roughly 24-30 times the slab thickness in feet: about 10 ft for a 4 in slab. Concrete cracks; joints decide where.
- The base has to be compacted in lifts, not dumped. An uncompacted base is the usual reason a good pour cracks in its first year.
- Thickened edges, footings and turndowns are extra concrete and are not included in this volume.
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