Thickness is the biggest factor in how much concrete you buy. Every extra inch on a 10 x 10 ft slab adds about 0.31 cubic yards.
| Project | Typical thickness |
|---|---|
| Walkway, patio | 4 in |
| Shed base | 4 to 6 in |
| Driveway, garage floor | 5 to 6 in |
| Heavy vehicles | 6 in or more, engineer-specified |
These are general figures. Soil, climate and local code can change them, so confirm with your building department. Reinforcement (wire mesh or rebar) and a compacted gravel base matter as much as thickness.
Use the slab calculator to compare thicknesses.