Concrete for a 20x20 Slab: Yards & Bags
A 20 × 20 ft slab at 4 inches thick is 4.94 cubic yards. With 10% extra for waste, plan on 5.43 cubic yards: 245 bags of 80 lb or 326 bags of 60 lb mix. Change the thickness below.
5.43 cubic yards of concrete
- Cubic yards
- 5.43
- Cubic feet
- 146.67
- 80 lb bags
- 245
- 60 lb bags
- 326
- 40 lb bags
- 489
- Includes 10% extra for spillage and uneven ground.
- Bag yields: 80 lb ≈ 0.60 cu ft, 60 lb ≈ 0.45 cu ft, 40 lb ≈ 0.30 cu ft.
- Over about 1 cubic yard, ready-mix delivery is usually cheaper and easier than mixing bags by hand.
Frequently asked questions
How many bags of concrete for a 20x20 slab?
About 245 bags of 80 lb concrete at 4 inches thick, including 10% extra.
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