Use this mulch calculator to find bulk cubic yards and whole bags from a bed's shape, dimensions, depth, and bag size. Choose a rectangle, circle, or tree ring so the measured space matches the volume calculation.
How to use the mulch calculator
Use this before buying mulch for a garden bed, landscape island, or tree ring. It estimates material quantity; it does not select a horticulturally appropriate material or replace site-specific tree-care guidance.
A tree ring subtracts the clear inner circle around the trunk; a plain circle does not.
For garden beds, Iowa State Extension gives general 2 to 4 guidance. Around trees and shrubs, Maryland Extension recommends a shallower 1 to 3 layer and a clear gap at the trunk.
Bag counts depend on cubic feet per bag, not the bag's weight. The calculator rounds up to a whole bag.
Example: a 20 × 5 ft bed at 3 in deep
- A 20 × 5 ft bed has 100 sq ft of area.
- At 3 in deep, it needs 25 cu ft, or 0.93 cu yd.
- With 2 cu ft bags, round up to 13 bags.
How mulch volume is calculated
The selected bed area is multiplied by depth after inches are converted to feet. Cubic feet are divided by 27 for cubic yards. A tree ring uses the outer circle minus the inner clear circle.
Bulk mulch and bagged mulch
Bulk suppliers usually quote cubic yards, while stores label bags in cubic feet. Both results describe the same entered volume; the bag result rounds up so it can be used as a purchase count.