How deep should topsoil be? Topsoil depth by project — topdressing, lawn, garden bed, raised bed

Topsoil depth is never one number — it tracks the project. Topdressing ¼–½″ per pass, a new lawn (seed or sod) 4–6″, garden beds 6–8″, raised beds 8–12″ for leafy crops and 12–24″ for deep-rooted. The calculator picks depth from the project type before it computes volume.

What this diagram shows

Five topsoil-filled columns of increasing height on a common ground line, showing the depth each project needs at one scale. Topdressing is a thin quarter-to-half-inch pass per application. A new lawn from seed or sod wants the same firmed 4-to-6-inch root zone because the soil prep is identical. A garden or flower bed takes 6 to 8 inches. A raised bed wants 8 to 12 inches for leafy crops and 12 to 24 inches for deep-rooted crops such as tomatoes and carrots. A caution notes topdressing must stay at a quarter to half inch per pass or thicker layers smother the turf, and that deep grade changes go to fill dirt with a topsoil cap. The calculator runs its cubic-yard math on this depth, so the project type sets the depth before any area math starts.