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Mulch Calculator
Find out how much mulch to buy for flower beds, borders and tree rings. Enter the size of the area and the depth you want, and the calculator returns cubic yards for bulk delivery and the number of 2 and 3 cubic foot bags.
Results are estimates. Soil, stone and mulch settle, weigh differently and vary by supplier. Confirm quantities and local requirements before ordering.
How to calculate it
Mulch is sold by volume, so the calculation is area × depth. Measure the length and width of each bed in feet, multiply to get square feet, then multiply by the depth in feet (3 inches = 0.25 ft). That gives cubic feet. Divide by 27 to get cubic yards, which is how bulk mulch is sold.
Formula: cubic yards = length (ft) × width (ft) × depth (in) ÷ 12 ÷ 27.
For round beds, use π × radius² for the area. For irregular beds, split the shape into rectangles, circles and triangles, calculate each one, and add them together. You can also use the "number of identical areas" box if you have several matching beds.
Worked example
A 30 ft × 8 ft border mulched 3 inches deep, with 5% extra:
| Area | 240 sq ft |
|---|---|
| Volume (no extra) | 60 cu ft 2.22 cubic yards |
| Bulk mulch to order | 2.33 cubic yards includes 5% extra |
| 2 cu ft bags | 32 bags |
| 3 cu ft bags | 21 bags |
| Cubic meters | 1.78 m³ |
How far does one cubic yard of mulch go?
| Depth | Coverage per cubic yard |
|---|---|
| 1 inch | 324 sq ft |
| 2 inches | 162 sq ft |
| 3 inches | 108 sq ft |
| 4 inches | 81 sq ft |
Tips
- Most beds do well with 2–3 inches of mulch. Going deeper than 4 inches can suffocate roots and hold too much moisture.
- Keep mulch a few inches away from tree trunks and house walls. A thick pile against the trunk invites rot and pests.
- Buy a little extra. Mulch settles and breaks down, and a top-up is cheaper to carry than a second delivery.
- Bulk mulch is usually cheaper than bags once you need more than about 2 cubic yards, but check the delivery fee.
Frequently asked questions
How many bags of mulch are in a cubic yard?
A cubic yard is 27 cubic feet. That is 13.5 bags of 2 cubic foot mulch or 9 bags of 3 cubic foot mulch. Always round up.
How deep should mulch be?
About 2–3 inches for most flower beds and shrubs. Thinner layers (1–2 inches) are enough when you are topping up existing mulch. Avoid layers over 4 inches.
How much does a cubic yard of mulch weigh?
It varies a lot with the type and how wet it is. As a rough guide, shredded bark and wood mulch are often between 400 and 800 lb per cubic yard. Check with your supplier if you are hauling it yourself.
Should I add extra for waste?
A 5–10% allowance is common. Uneven ground, settling and spillage all use up more than the pure area × depth figure.