Enter your slab or footing dimensions to get the concrete volume in cubic yards and cubic feet, plus the number of 40, 50, 60, and 80 lb bags. One 80 lb bag of concrete mix yields about 0.6 cubic feet.
You need approximately
1.23 cubic yards
33.33 ft³ of concrete
With 5% waste: 1.3 cubic yards(recommended when ordering)
40 lb bags
112 bags
50 lb bags
89 bags
60 lb bags
75 bags
80 lb bags
56 bags
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Why order extra? The headline number is the exact material your project
needs. When you actually order, add about 5–10% on top — the “with 5% waste” figure
in the result is a safe starting point. That margin covers what you lose to compaction,
cuts around edges and corners, and ordinary spillage during handling. It is cheaper to have
a little left over than to stop mid-job and wait on a second delivery.
Field notes
Past about 50 bags, stop bagging and order ready-mix — hand-mixing that volume risks cold joints between batches and eats a whole day. Order 5–10% over; you can't pause a pour to run for more, and a short load means a visible seam. Dampen the subgrade and set your forms dead level first, because concrete finds every low spot and won't forgive a sloppy base.
Multiply length × width × thickness in feet and divide by 27. A 10 × 10 ft slab at 4 inches thick needs about 1.23 cubic yards of concrete.
How many 80 lb bags of concrete are in a cubic yard?
It takes about 45 bags of 80 lb concrete mix to make one cubic yard, since each 80 lb bag yields roughly 0.6 cubic feet.
How much concrete for a 10x10 slab?
A 10×10 ft slab poured 4 inches thick needs about 1.23 cubic yards (33.3 cubic feet) of concrete — roughly 56 bags of 80 lb mix, though ready-mix delivery is usually cheaper at this size.