Mulch Calculator
To calculate mulch, multiply the bed length by width to get the area, then by depth in feet, and divide by 27 for cubic yards. A 20×4 ft bed at 3 inches deep needs about 0.74 cubic yards (roughly 10 bags), costing about $22–$37 in bulk mulch.
- Ideal depth
- 2–3 in
- 1 yd³ at 3 in
- 108 ft²
- Bag size
- 2 ft³
Your measurements
2–3 in is typical for beds; 1 in for refresh.
Enter your measurements
Fill in the fields to see your estimate.
The formula
Mulch (yd³) = (Length ft × Width ft × Depth ft) ÷ 27How to calculate it manually
- 1
Measure the bed
Record length and width in feet.
- 2
Choose a depth
Convert inches to feet (3 in = 0.25 ft).
- 3
Find the volume
Multiply area × depth for cubic feet.
- 4
Convert to yards
Divide cubic feet by 27, or by 13.5 for 2 ft³ bags.
Example calculation
A 20 ft × 4 ft bed at 3 in deep: 80 ft² × 0.25 ft = 20 ft³ ÷ 27 ≈ 0.74 yd³ (≈ 10 bags).
Mulch coverage by depth
Area that one cubic yard of mulch covers at different depths.
| Depth | Coverage per yd³ | Bags (2 ft³) per yd³ |
|---|---|---|
| 1 inch | 324 ft² | ~13.5 |
| 2 inches | 162 ft² | ~13.5 |
| 3 inches | 108 ft² | ~13.5 |
| 4 inches | 81 ft² | ~13.5 |
Common mulch estimating mistakes
Mulching too deep
More than 3–4 inches suffocates roots and holds excess moisture. Two to three inches is the sweet spot.
Piling mulch against stems
"Mulch volcanoes" around trunks invite rot and pests. Keep mulch a few inches clear of stems and trunks.
Ignoring existing mulch
If a bed already has mulch, you usually only need a 1-inch refresh — measure for the top-up, not the full depth.
Buying bags for big beds
For large areas, bulk mulch by the cubic yard is far cheaper than bagged. Compare price per cubic foot.
Frequently asked questions
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