Mulch Calculator
Mulch serves multiple purposes in garden beds: it suppresses weeds, retains soil moisture, moderates soil temperature, and slowly adds organic matter as it breaks down. Buying the right amount is important because bulk mulch is sold by the cubic yard and bagged mulch by the cubic foot, which can cause confusion when planning a purchase. This mulch calculator converts your bed area and desired depth into both cubic yards and cubic feet, so you can easily compare bulk versus bagged options. You can enter either total area in square feet or the individual length and width of a rectangular bed, whichever is easier. The default depth is 3 inches, which is widely recommended by extension services for most ornamental garden beds. One cubic yard of mulch covers 324 square feet at 1 inch deep, 162 square feet at 2 inches deep, or 108 square feet at 3 inches deep. The calculator also shows how many 2 cubic foot bags you would need as an alternative to bulk delivery. When mulching around trees, add the area of the mulch ring but remember to keep mulch away from the trunk itself. For multiple separate beds, add up their individual areas before entering the total, or run the calculator separately for each bed.
Mulch calculation formula
Cubic feet = Area (sq ft) x Depth (ft)
Cubic yards = Cubic feet / 27
2 cu ft bags = ceil(Cubic feet / 2)
Coverage: 1 cu yd covers 324 sq ft at 1 inch deep
Quick coverage reference
| Depth | 1 cu yd covers | 1 cu ft covers |
|---|---|---|
| 1 inch | 324 sq ft | 12 sq ft |
| 2 inches | 162 sq ft | 6 sq ft |
| 3 inches | 108 sq ft | 4 sq ft |
| 4 inches | 81 sq ft | 3 sq ft |
Mulch calculator: frequently asked questions
How much mulch do I need per square foot?
The amount of mulch depends on the desired depth. One cubic yard of mulch covers 324 square feet at 1 inch deep, 162 square feet at 2 inches deep, 108 square feet at 3 inches deep, or 81 square feet at 4 inches deep. For most garden beds, 2 to 3 inches of mulch is recommended. This calculator converts your area and desired depth directly to cubic yards.
How deep should mulch be in garden beds?
The University of Maryland Extension and most cooperative extension services recommend 2 to 3 inches of mulch for established garden beds. Too little (under 2 inches) allows weeds through and dries out quickly. Too much (over 4 inches) can suffocate roots and harbour pests and disease. Keep mulch pulled back 2 to 3 inches from plant stems and tree trunks to prevent crown rot.
How many bags of mulch equal a cubic yard?
Most bagged mulch sold at home improvement stores comes in 2 cubic foot bags. One cubic yard equals 27 cubic feet, so you would need about 13.5 bags (round up to 14) to fill one cubic yard. Some bags are 3 cubic feet, which means you need 9 bags per cubic yard. Check the bag label for the cubic footage of each bag.
Is bulk or bagged mulch cheaper?
Bulk mulch (delivered by the cubic yard) is almost always cheaper per cubic foot than bagged mulch, especially for quantities of 2 or more cubic yards. Bagged mulch is more convenient for small areas or when you need to spread it over multiple separate beds. The trade-off is that bulk mulch requires a delivery fee and a place to dump the pile near where it will be used.
What type of mulch is best for garden beds?
Shredded hardwood bark and wood chip mulch are the most common and widely recommended for perennial garden beds because they decompose slowly, suppress weeds, and improve soil structure over time. Pine bark nuggets drain well but can float in heavy rain. Straw mulch works well for vegetable gardens. Rubber mulch is long-lasting but does not improve soil. For advice specific to your region, contact your local cooperative extension service.
Sources
- University of Maryland Extension, mulching guidelines: extension.umd.edu.
- USDA Forest Service urban forestry and mulch guidance: fs.usda.gov.
Reviewed by the CalculatorHub team, edited by James Graham, 14 June 2026. See our methodology. Consult your local cooperative extension for regional guidance.