6×6 slab: concrete by thickness
| Thickness | Cu ft | Cu yd | 80 lb bags | 60 lb bags |
|---|---|---|---|---|
| 3.5″ | 10.50 | 0.39 | 18 | 24 |
| 4″ | 12.00 | 0.44 | 20 | 27 |
| 5″ | 15.00 | 0.56 | 25 | 34 |
| 6″ | 18.00 | 0.67 | 30 | 40 |
No waste included in the table.
Worked example
6 ft × 6 ft = 36 sq ft. At 4 inches: 36 × 4 ÷ 12 = 12.00 cu ft, or 0.44 cubic yards. With 10% extra that is 0.49 yd³, or 22 bags of 80 lb mix.
At this size, bagged mix is manageable by hand.
Assumes standard concrete mix bag yields: 80 lb ≈ 0.60 cu ft, 60 lb ≈ 0.45 cu ft. Check the yield on your bag. 1 cubic yard = 27 cubic feet.
Frequently asked questions
How many bags of concrete for a 6×6 slab?
20 × 80 lb or 27 × 60 lb bags at 4 inches thick, before waste.
How many yards of concrete for a 6×6 slab?
0.44 cubic yards at 4 inches; 0.67 at 6 inches.