Concrete for a 30x40 Slab: Yards & Bags
A 30 × 40 ft slab at 4 inches thick is 14.81 cubic yards. With 10% extra for waste, plan on 16.3 cubic yards: 734 bags of 80 lb or 978 bags of 60 lb mix. Change the thickness below.
16.3 cubic yards of concrete
- Cubic yards
- 16.3
- Cubic feet
- 440
- 80 lb bags
- 734
- 60 lb bags
- 978
- 40 lb bags
- 1,467
- 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 30x40 slab?
About 734 bags of 80 lb concrete at 4 inches thick, including 10% extra.
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