Mulch Calculator
Work out exactly how many cubic yards or bags of mulch you need for your garden beds, based on your bed sizes and desired depth. Add your own price for a full cost estimate.
How this calculator works
The calculator finds the volume of mulch needed to cover your beds at the depth you specify, then converts it to cubic yards or bags:
volume = bed area × (depth ÷ 12) cubic yards = volume ÷ 27 bags = ceil( volume ÷ bag size )
Worked example
A 20 ft × 10 ft bed, 3 inches deep:
- Bed area: 20 × 10 = 200 sq ft.
- Volume: 200 × (3 ÷ 12) = 50 cu ft.
- In cubic yards: 50 ÷ 27 ≈ 1.85, rounded up to 1.86 cu yd.
- In 2 cu ft bags: 50 ÷ 2 = 25 bags.
How deep should mulch be?
| Use | Typical depth | Notes |
|---|---|---|
| Perennial and flower beds | 2–3" | Enough to suppress weeds without smothering shallow roots |
| Shrub borders | 3" | Standard depth for most landscape beds |
| Tree rings | 3–4" | Wide ring, kept clear of the trunk itself |
| Annual refresh layer | 1" | Topping up mulch that hasn't fully broken down |
Piling mulch directly against a trunk or stems — often called "volcano mulching" — traps moisture against the bark and can encourage rot and pests, so keep a small gap clear even within a mulched ring.
Bulk vs bags
Bagged mulch costs more per cubic yard than bulk, often substantially more, but doesn't require a delivery minimum or anywhere to store a pile. As a rough guide, projects needing more than 2 to 3 cubic yards usually work out cheaper with bulk delivery even after any delivery fee, while smaller beds are often easiest handled with a handful of bags from a local supplier.
Frequently asked questions
How deep should mulch be around plants vs trees?
2 to 3 inches is typical around perennials, shrubs and garden beds — enough to suppress weeds and retain moisture without smothering shallow roots. Around trees, a wider ring of 3 to 4 inches is common, but mulch should never be piled directly against the trunk.
When does bulk mulch become cheaper than bags?
Bagged mulch is usually more expensive per cubic yard than bulk, but bulk typically needs a delivery minimum and somewhere to store it. As a rough guide, once a project needs more than 2 to 3 cubic yards, bulk delivery usually works out cheaper even after any delivery fee.
How often should mulch be topped up?
Organic mulch like bark or wood chips typically breaks down enough to need topping up once a year, often in spring. A thin refresh layer of about 1 inch is usually enough if the existing mulch hasn't fully decomposed.
Does mulch color or type change how much I need?
No — dyed and natural mulches, and most bark, wood chip or shredded types, are sold and measured by volume the same way, so quantity depends only on area and depth, not color or material. Denser materials like rubber mulch are the main exception, since they're sometimes sold by weight instead.