How many bags of concrete for a 8x10 slab, 4 inches thick?
A 8x10 slab 4 inches thick needs 26.7 cubic feet (0.99 cubic yards) of concrete: about 49 bags of 80 lb mix with 10% extra.
| Bag size | Exact | With 10% extra |
|---|---|---|
| 80 lb | 45 | 49 |
| 60 lb | 60 | 66 |
| 50 lb | 72 | 79 |
| 40 lb | 89 | 98 |
Typical yields: 80 lb bag 0.60 cu ft, 60 lb 0.45, 50 lb 0.375, 40 lb 0.30. Check your bag; brands vary slightly. The 10% covers spills, uneven ground and form flex.