Mulch and Topsoil Calculator
Cubic yards and bags of mulch, topsoil or compost for a bed, plus guidance on the depth that actually helps.
Mulch & Topsoil Calculator
Cubic yards, bags and what depth to actually use. Depth is the part that matters — too thin does nothing for weeds, too thick suffocates the roots you were trying to protect.
| Bed area | — |
|---|---|
| Volume | — |
| Cubic yards | — |
| Bags | — |
| Bulk vs bagged | — |
One cubic yard is 27 ft³, so a 100 ft² bed at 3″ deep works out at
25 ft³ — about 0.93 yd³, or roughly 13 two-cubic-foot bags. That arithmetic is exact.
Depth is a judgement, not a formula. Two to three inches of mulch is a normal refresh; three to
four suppresses weeds and holds moisture better. Deeper is not better — piling mulch against a
trunk in a mound traps moisture against the bark and invites rot, which is why arborists keep telling
people to pull it back from the stem. Topsoil and compost depths depend entirely on what you are
growing and what is underneath. Bulk delivery usually beats bags somewhere around a cubic yard, but
minimum delivery charges vary, so compare both.