| Project | Typical thickness | Base |
|---|---|---|
| Sidewalk, patio | 4 in | 4 in compacted gravel |
| Shed base | 4 in | 4 in gravel |
| Hot tub pad | 4–6 in | check the tub’s spec |
| Driveway (cars) | 5–6 in | 4–6 in gravel |
| Garage floor | 5–6 in | 4 in gravel |
| RV or heavy truck pad | 6–8 in | 6 in gravel, rebar |
Local codes and your engineer’s plans override these typical figures. Use the gravel calculator for the base and the concrete calculator for the slab.