Bags or a truck?
At this size a ready-mix truck is the sensible choice. Mixing 80 bags by hand is a long, heavy day, and the first batches start to set before the last ones are placed.
Concrete slab charts · 12 × 12 ft
How much concrete for a 12×12 slab?
A 12 × 12 ft slab 4 inches thick needs 1.78 cubic yards of concrete (48.0 cubic feet), or about 80 bags of 80 lb premix. Add 5–10% for waste. Other thicknesses are in the table, or adjust the calculator below.
Units
12 × 12 ft slab by thickness
Exact volumes without waste. Bag counts are rounded up.
| Thickness | Cubic yards | Cubic feet | 80 lb bags | 60 lb bags | Metric |
|---|---|---|---|---|---|
| 3 in | 1.33 yd³ | 36.0 ft³ | 60 | 80 | 1.02 m³ |
| 4 in | 1.78 yd³ | 48.0 ft³ | 80 | 107 | 1.36 m³ |
| 5 in | 2.22 yd³ | 60.0 ft³ | 100 | 134 | 1.70 m³ |
| 6 in | 2.67 yd³ | 72.0 ft³ | 120 | 160 | 2.04 m³ |