Mulch Calculator
A 20×8 ft garden bed at 3 in deep needs 1.5 cu yd of mulch ($40–$80 bulk, or 20 retail bags). Enter your bed size and mulch type for an exact estimate.
Inputs
Estimate
- Bed area160 sq ft
- Cubic yards needed1.48cu yd
- 2 cu ft bags neededStandard retail mulch bag = 2 cubic feet.20bags
- Bulk mulch cost — low$37
- Bulk mulch cost — high$74
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Try Remodel AI freeHow to calculate mulch needed
Mulch is measured in cubic yards for bulk delivery and 2-cubic-foot bags for retail purchase. To calculate cubic yards, multiply length × width × depth (in feet), then divide by 27 (since 1 cubic yard = 27 cubic feet). Depth should be in feet — divide the inches by 12.
Standard mulch depth: 2 inches for maintenance topping over existing mulch. 3 inches for fresh installation. 4+ inches for heavy weed suppression. Don't pile mulch against tree trunks — keep 2–3 inches clear around the base to prevent rot.
Bulk mulch is much cheaper than bagged for any project over 1 cubic yard. A pickup truck holds 1.5–2 cu yd of mulch. SUVs and small cars are not suitable for bulk delivery.
Formulas used
- Cubic yards
(length × width × depth_inches/12) / 27Volume in cubic feet divided by 27 = cubic yards. - 2 cu ft bags
cubic_feet / 2Standard retail bag = 2 cu ft. Bulk = cubic yards.
Frequently asked questions
How many cubic yards of mulch do I need?+
Multiply length × width × depth-in-feet, then divide by 27. A 20×8 ft bed at 3 inches deep = (20 × 8 × 0.25) / 27 = 1.48 cubic yards. Use the calculator above for exact amounts.
How many bags of mulch in a cubic yard?+
13.5 bags of 2-cubic-foot mulch = 1 cubic yard. So a 1.5 cubic yard project = 20 bags.
How thick should mulch be?+
3 inches for new installation. 2 inches for refresh over existing mulch. 4+ inches for heavy weed suppression — but don't exceed 4 inches around plants, it can suffocate roots.
How much does a cubic yard of mulch cost?+
Bulk hardwood mulch: $25–$50/cu yd. Dyed mulch: $30–$60. Cedar: $40–$75. Pine bark: $30–$60. Rubber mulch: $100–$200. Bagged mulch is 30–50% more expensive per cubic yard.
When should I mulch?+
Best time: mid-to-late spring after soil warms. Worst time: fall in cold climates — wet mulch over frozen plants can cause root damage. Apply or refresh annually in spring.