A 12 ft by 20 ft slab covers 240 square feet. At 4 inches thick it holds 80 cubic feet of concrete, which is 2.96 cubic yards, or 3.26 cubic yards with 10% extra.
Volume by thickness
| Thickness | Cubic feet | Cubic yards | With 10% extra (cu yd) |
|---|---|---|---|
| 4 in | 80 | 2.96 | 3.26 |
| 5 in | 100 | 3.7 | 4.07 |
| 6 in | 120 | 4.44 | 4.89 |
Bags by yield and thickness
Bags differ, so the table shows three yields. Find the yield printed on your bag. Counts include 10% extra and round up.
| Bag yield | 4 in | 5 in | 6 in |
|---|---|---|---|
| 0.5 cu ft | 176 | 220 | 264 |
| 0.6 cu ft | 147 | 184 | 220 |
| 0.8 cu ft | 110 | 138 | 165 |
Check it with your own numbers
If your slab is not exactly 12 by 20 ft, use the concrete calculator. For the base under it, see the gravel calculator.
Nearby sizes
- 16 by 16 ft slab: 256 square feet.
- 12 by 16 ft slab: 192 square feet.
- 12 by 12 ft slab: 144 square feet.
- All slab sizes