How to use this mulch calculator
This mulch calculator helps gardeners, landscape contractors, and DIY homeowners figure exactly how much mulch, bark, woodchips, or topsoil is needed for garden beds and borders. Enter your garden bed length, width, target mulch layer thickness (typically 2 to 3 inches for weed suppression and moisture conservation), and compare costs between bagged mulch and bulk landscape delivery.
Mulch coverage and volume formulas
Standard landscape equations for calculating mulch:
A convenient shortcut: multiply Length (ft) × Width (ft) × Depth (in), then divide by 324 to get cubic yards in one step.
Mulch coverage reference chart (Common Garden Bed Sizes)
| Garden Bed Area (ft²) | Cubic Yards (at 2" depth) | Cubic Yards (at 3" depth) | 2 cu ft Bags (at 3" depth) | 3 cu ft Bags (at 3" depth) |
|---|---|---|---|---|
| 50 ft² | 0.31 yd³ | 0.46 yd³ | 7 bags | 5 bags |
| 100 ft² (e.g. 20×5 ft) | 0.62 yd³ | 0.93 yd³ | 13 bags | 9 bags |
| 200 ft² (e.g. 40×5 ft) | 1.23 yd³ | 1.85 yd³ | 25 bags | 17 bags |
| 500 ft² (large border) | 3.09 yd³ | 4.63 yd³ | 63 bags | 42 bags |
| 1,000 ft² (full landscape) | 6.17 yd³ | 9.26 yd³ | 125 bags | 84 bags |
Step-by-step worked mulch calculation example
Here is how to figure mulch for a 20 ft by 5 ft garden planting border at a recommended 3-inch depth:
- Calculate surface area: 20 ft × 5 ft = 100 square feet.
- Convert depth to feet: 3 inches ÷ 12 = 0.25 feet.
- Calculate cubic feet: 100 sq ft × 0.25 ft = 25 cubic feet.
- Convert to cubic yards: 25 cu ft ÷ 27 = 0.93 cubic yards.
- Determine bag requirements: At 2 cubic feet per bag (standard store bags), 25 ÷ 2 = 12.5, which rounds up to 13 bags. At .50 per bag, total cost is .50.
Bagged mulch vs. bulk delivery: Which is better?
If your project requires less than 2 cubic yards (under 27 standard 2-cu-ft bags), buying bagged mulch at your local home improvement center is usually cheaper, easier to transport in a trunk or SUV, and cleaner to store. For larger projects requiring 3 or more cubic yards, ordering bulk mulch from a local landscape supplier is significantly cheaper per yard and eliminates plastic bag waste, though delivery fees usually range from to .
Frequently asked questions about mulch
How deep should mulch be?
A depth of 2 to 3 inches is ideal for most flowerbeds and vegetable gardens. This depth effectively prevents weed growth, retains soil moisture, and moderates root temperature. Avoid applying deeper than 4 inches, as excessive mulch can trap too much moisture and suffocate shallow root systems.
How many bags of mulch make a cubic yard?
One cubic yard (27 cubic feet) equals exactly 13.5 bags of 2-cubic-foot mulch, or 9 bags of 3-cubic-foot mulch.
Should mulch touch tree trunks or plant stems?
No. Keep mulch 2 to 3 inches away from the base of woody plant stems and tree trunks to create a 'donut' rather than a 'mulch volcano'. Mulch piled against tree bark fosters fungal rot and invites burrowing insects.
Looking for soil for raised garden beds?
If you are filling deep wooden or corrugated garden beds with custom soil blends, use our companion Raised-bed soil calculator.
Created and calculation-tested by Velour Trends · Updated 8 November 2026. Standard volumetric formulas verified. Report a calculation issue.