PourGaugeHow much concrete you actually need, and what to mix into it.

How much concrete for a 26 × 32 ft slab, 5″ thick?

Concrete needed
14.12cubic yards
381.33 ft³ including 10% waste
Plan26 ft32 ft832 ft²SectionConcrete slab — 5″Compacted gravel base — 4″
Slab area832ft²
Volume (exact)before waste346.67ft³
Volume (order this)+10% waste381.33ft³
Ready-mix14.12yd³
40 lb bags0.3 ft³ per bag1,272bags
60 lb bags0.45 ft³ per bag848bags
80 lb bags0.6 ft³ per bag636bags
Gravel base (4")10.27yd³
Rebar #4 @ 18" grid1,206linear ft

Notes

  • At 14.12 yd³ a ready-mix truck is almost always cheaper than bagged mix — most suppliers have a 1 yd³ minimum plus a short-load fee.
  • Figures assume a flat slab on a compacted base. Thickened edges, footings and piers need to be added separately.

How the number is worked out

A 26 × 32 ft slab covers 832 ft². At 5 inches thick that is 381.33 ft³ of concrete once 10% is added for waste — spillage, an uneven base and overfill at the form edges.

Divided by 27, that comes to 14.12 cubic yards.

Bags or ready-mix

Bagged mix is priced per bag and mixed on site; ready-mix arrives in a truck already wet. The crossover sits close to 1 cubic yard. Below it, bags usually win. Above it, the short-load fee on a small delivery is still cheaper than 636 bags and the hours it takes to mix them.

What is not included

These figures are for a flat slab on a compacted base. Thickened edges, footings, piers and any slope have to be added on top.

Nearby sizes

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