Mulch Calculator
Enter the dimensions of your garden bed and desired mulch depth to calculate how much mulch you need in cubic yards and bags.
How Mulch Calculator works
How mulch volume is calculated
Volume = Length × Width × Depth. Convert depth from inches to feet (divide by 12), calculate in cubic feet, then divide by 27 to get cubic yards. One cubic yard of mulch covers approximately 162 sq ft at 2 inches deep, 108 sq ft at 3 inches, or 81 sq ft at 4 inches.
Recommended mulch depth
Most landscaping guides recommend 2–4 inches of mulch. Use 2 inches around established perennials and annuals, 3 inches for general landscape beds, and 4 inches for weed suppression and moisture retention in areas without dense planting. Do not pile mulch against tree trunks or house siding — keep a 3–6 inch gap ("volcano mulching" damages trees).
Types of mulch
Organic mulches (hardwood, pine bark, cedar, cypress) decompose over time, improving soil structure. They need replenishing annually. Inorganic mulches (rubber, stone) last longer but don't improve soil. For most garden beds, shredded hardwood is the most popular choice — it stays in place well, looks neat, and enriches the soil as it decomposes.
Bulk vs bagged mulch
Bulk mulch is sold by the cubic yard and delivered by truck. It costs $25–$45 per cubic yard plus delivery ($50–$150 depending on distance). Bagged mulch from a garden centre costs $3–$7 per 2 cu ft bag, equivalent to $40–$95 per cubic yard. Bulk is more economical for areas needing more than 2–3 cubic yards.
When to mulch
The best time to apply mulch is in late spring after the soil has warmed. Adding mulch too early in spring keeps soil cold and delays plant growth. In autumn, mulch protects roots from freeze-thaw cycles. Replenish organic mulch annually as it breaks down — top up to maintain the recommended depth.
Frequently asked questions
How much mulch do I need for a flower bed?
A typical 20×8 ft flower bed at 3 inches deep needs about 1.5 cubic yards (40 cubic feet) of mulch, or 20 standard 2 cu ft bags. Measure your bed's length and width, choose a depth of 2–4 inches, and enter the dimensions above.
How many bags of mulch in a cubic yard?
One cubic yard = 27 cubic feet. A standard mulch bag is 2 cubic feet, so you need 13.5 bags (round up to 14) per cubic yard. For 3 cu ft bags, you need 9 bags per cubic yard.
How deep should mulch be?
2–3 inches for most garden beds. Use 4 inches for heavy weed suppression or areas with poor soil. Never exceed 4 inches — too-deep mulch can suffocate roots and create moisture problems. Keep mulch 3–6 inches away from tree trunks and plant stems.
How much does a yard of mulch cost?
Bulk mulch costs $25–$45 per cubic yard for common varieties (hardwood, pine). Premium mulches (cedar, coloured) cost $35–$65 per yard. Delivery typically adds $50–$150. Bagged mulch from stores costs effectively $40–$95 per cubic yard but has no delivery fee.
How often should I replace mulch?
Organic mulch (wood, bark) should be replenished annually. It decomposes over 1–2 years, enriching the soil in the process. Before adding new mulch, rake the existing layer to break up matted sections. You don't need to remove old mulch — just top up to maintain 2–3 inches total depth.
What is the best mulch for weed control?
Shredded hardwood or double-shredded mulch at 3–4 inches deep is the most effective organic option for weed suppression. It mats together well and blocks light. For permanent weed barrier, lay landscape fabric under the mulch. Rubber mulch lasts longest but doesn't improve soil and can smell in hot weather.
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