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

How much concrete for a 10 × 24 ft slab, 5″ thick?

Concrete needed
4.07cubic yards
110 ft³ including 10% waste
Plan10 ft24 ft240 ft²SectionConcrete slab — 5″Compacted gravel base — 4″
Slab area240ft²
Volume (exact)before waste100ft³
Volume (order this)+10% waste110ft³
Ready-mix4.07yd³
40 lb bags0.3 ft³ per bag367bags
60 lb bags0.45 ft³ per bag245bags
80 lb bags0.6 ft³ per bag184bags
Gravel base (4")2.96yd³
Rebar #4 @ 18" grid362linear ft

Notes

  • At 4.07 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 10 × 24 ft slab covers 240 ft². At 5 inches thick that is 110 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 4.07 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 184 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

Read more