Mulch Calculator
Find out exactly how much mulch you need for garden beds, trees, or landscaping — in cubic yards, cubic feet, or bags.
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How Much Mulch Do I Need?
The formula for mulch is simple: multiply your bed's length by its width to get the area, then multiply by the desired depth. Because mulch is sold by the cubic yard in the US (and by the cubic metre in the UK), the calculator converts the final volume into the right unit automatically.
For most garden beds, 3 inches (7.5 cm) is the sweet spot — deep enough to suppress weeds and retain moisture, but not so thick that water can't reach the roots. A 2-inch layer works well for annual refreshes when some old mulch is still in place.
Mulch Depth Reference Guide
| Depth | Best For | Cu Yds per 100 sq ft |
|---|---|---|
| 1 inch | Light refresher, thin top-up | 0.31 |
| 2 inches | Annual maintenance layer | 0.62 |
| 3 inches | New beds – recommended depth | 0.93 |
| 4 inches | Heavy weed suppression | 1.23 |
Types of Mulch and How They Affect Volume
The type of mulch doesn't change the volume calculation, but it does affect how much it settles over time. Shredded wood and bark mulch can compress by 10–15% after rain, which is why adding a 10% overage is the standard recommendation. Rubber mulch settles very little. Stone and gravel don't compress at all but are harder to spread evenly on slopes.
Bags vs. Bulk Delivery
In the US, mulch is sold in 2 cu ft bags at most hardware stores (Home Depot, Lowe's). Bulk delivery by the cubic yard becomes cost-effective for orders above 3–4 cubic yards. In the UK, mulch is typically sold in 60-litre bags. The calculator shows both bag sizes to cover the most common options in each market.
Tips for a Professional Finish
Keep mulch 2–3 inches away from plant stems and tree trunks to prevent rot. Rake and loosen old mulch before adding a fresh layer. For sloped beds, use shredded bark rather than wood chips, which tend to wash away. Edge your beds with a spade before mulching for a clean, defined border.