Concrete Quick Reference: Common Slab Sizes
All figures are at 4-inch depth with a 10% waste buffer included. Ready-mix is typically ordered by the cubic yard; bags are the alternative for small pours.
Rule of thumb: anything under 1 cubic yard — use bags. Above 1 yard — ready-mix truck is more economical.
| Slab size | Cubic yards | 60 lb bags | 80 lb bags |
|---|---|---|---|
| 10×10 ft | 1.23 yd³ | 72 | 56 |
| 10×20 ft | 2.47 yd³ | 145 | 112 |
| 12×12 ft | 1.78 yd³ | 105 | 81 |
| 12×16 ft | 2.37 yd³ | 140 | 108 |
| 20×20 ft | 4.94 yd³ | 291 | 225 |
| 20×30 ft | 7.41 yd³ | 436 | 337 |
| 24×24 ft | 7.11 yd³ | 418 | 323 |
| 30×30 ft | 11.1 yd³ | 654 | 505 |
For other depths
Multiply cubic yards by: 0.75× for 3-inch depth · 1.25× for 5-inch depth · 1.5× for 6-inch depth. Or use the Concrete Calculator below for any dimension.