Mulch Calculator
How much mulch a garden bed needs, in cubic yards for bulk delivery or standard 2 cu ft bags, worked out from the bed size and the depth you want.
Results
Cubic yards
1.11yd³
2 cu ft bags
15bags
Volume
30ft³
Bulk mulch by the cubic yard is usually cheaper past about 200 sq ft of bed. Bags, at the standard 2 cu ft, are easier to handle on smaller or awkwardly shaped beds.
How the mulch calculator works
Mulch is a volume calculation, same as gravel or concrete. Multiply the bed length and width by the depth you want, then convert into the units mulch is sold in: cubic yards for bulk delivery, or 2 cu ft bags off the shelf.
Formula: volume (ft³) = length × width × (depth ÷ 12). Cubic yards = volume ÷ 27. Bags = volume ÷ 2 (rounded up, since bags come whole).
Mulching a round tree ring or a triangular corner bed? The Cubic Yard Calculator takes circles and triangles and gives the same cubic yards and bag count.
For lawn areas next to the beds, the Sod Calculator works out slabs, rolls and pallets.
Frequently asked questions
2-3 inches. That is enough to hold moisture in and keep weeds down, without burying roots or piling against trunks. Deeper is not better here: mulch heaped against a tree trunk holds damp bark against the tree and rots it.
13.5 bags, at the standard 2 cubic foot bag size, because a cubic yard is 27 cubic feet. In practice you buy 14. The calculator above works it out from your bed size so you do not have to.
Bulk, by a good margin, once you are past about 3-4 cubic yards. Below that, delivery minimums eat the saving and bags are easier to move around a garden anyway. Bags also win for small or awkwardly shaped beds, where a dumped pile is more work than it saves.
Usually not. A couple of inches of old, broken-down mulch is fine to top up over. Once the total gets past 4-5 inches, rake some out first, because a thick mat of old mulch sheds water instead of letting it through to the roots.
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