20x24 concrete slab
For a 20 by 24 foot slab at 4 inches thick, you need about 294 bags of 80 lb concrete mix, costing about $1,758.12.
Concrete slab
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Bags needed
29480 lb bags
= 392 x 60 lb bags
About $1,758.12 in 80 lb bags
= 5.93 cu yd ready-mix
Avg US retail price, checked Aug 2026.
If you are pouring a driveway, consider 6 inches thick. At that thickness, you will need about 440 bags of 80 lb mix.
This slab needs about 5.93 cubic yards, and you order ready mix concrete in cubic yards.
Bag prices are a US average, last checked Aug 2026.