Bags or a truck?
At this size a ready-mix truck is the sensible choice. Mixing 112 bags by hand is a long, heavy day, and the first batches start to set before the last ones are placed.
Concrete slab charts · 10 × 20 ft
How much concrete for a 10×20 slab?
A 10 × 20 ft slab 4 inches thick needs 2.47 cubic yards of concrete (66.7 cubic feet), or about 112 bags of 80 lb premix. Add 5–10% for waste. Other thicknesses are in the table, or adjust the calculator below.
Units
10 × 20 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 | 1.85 yd³ | 50.0 ft³ | 84 | 112 | 1.42 m³ |
| 4 in | 2.47 yd³ | 66.7 ft³ | 112 | 149 | 1.89 m³ |
| 5 in | 3.09 yd³ | 83.3 ft³ | 139 | 186 | 2.36 m³ |
| 6 in | 3.70 yd³ | 100.0 ft³ | 167 | 223 | 2.83 m³ |