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4×6 slab: concrete by thickness
| Thickness | Cu ft | Cu yd | 80 lb bags | 60 lb bags |
|---|---|---|---|---|
| 3.5″ | 7.00 | 0.26 | 12 | 16 |
| 4″ | 8.00 | 0.30 | 14 | 18 |
| 5″ | 10.00 | 0.37 | 17 | 23 |
| 6″ | 12.00 | 0.44 | 20 | 27 |
No waste included in the table.
Worked example
4 ft × 6 ft = 24 sq ft. At 4 inches: 24 × 4 ÷ 12 = 8.00 cu ft, or 0.30 cubic yards. With 10% extra that is 0.33 yd³, or 15 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 4×6 slab?
14 × 80 lb or 18 × 60 lb bags at 4 inches thick, before waste.
How many yards of concrete for a 4×6 slab?
0.30 cubic yards at 4 inches; 0.44 at 6 inches.