Guide
How much mulch do I actually need?
Updated May 2026 6 min read
The short answer: 1 cubic yard of mulch covers 108 sq ft at 3 inches deep. That's roughly a 9 ft × 12 ft bed, or 13.5 standard 2-cu-ft bags.
The longer answer depends on your bed shape, depth, and whether you're refreshing an existing bed or building one from scratch. This page walks through the full math, then points you at the mulch calculator when you've got real measurements.
Bag count by bed size
Rectangular beds at 3" depth, +10% settling buffer.
| Bed (ft) | Cubic yards | Bags @ 2 cu ft | Bags @ 3 cu ft |
|---|---|---|---|
| 4×4 | 0.15 | 2 | 2 |
| 4×8 | 0.30 | 4 | 3 |
| 8×10 | 0.74 | 10 | 7 |
| 10×10 | 0.93 | 13 | 9 |
| 10×20 | 1.85 | 25 | 17 |
| 20×20 | 3.70 | 50 | 34 |
1"
RefreshTopping up an established bed annually.
3"
StandardNew bed, average weed pressure.
4"
HeavyHigh weed pressure, slope retention.
FAQ
How many bags of mulch in a yard?
A cubic yard equals 27 cubic feet. That's 13.5 bags at 2 cu ft, 9 bags at 3 cu ft, or 18 bags at 1.5 cu ft.
How deep should mulch be?
Existing beds: 1-2 inches refresh. New beds: 3 inches standard, 4 inches if you have weed pressure. Never more than 4" — it suffocates roots.
What's a yard of mulch cover at 3"?
A cubic yard at 3" depth covers 108 square feet — about a 9×12 ft bed.
How many bags of mulch for a 10×10 bed?
At 3" depth: 0.93 cu yd, or 13 bags @ 2 cu ft / 9 bags @ 3 cu ft. With 10% settling buffer included.
How many bags of mulch for a 4×8 raised bed?
At 3" depth: 0.30 cu yd, or 4 bags @ 2 cu ft / 3 bags @ 3 cu ft.
Bulk vs bagged — which is cheaper?
Bulk wins above ~3 cu yd (≈40 bags @ 2 cu ft). Below that, bagged usually wins on convenience and avoids the $50-$100 delivery fee.
When should I mulch in spring?
After soil warms above 55°F (Apr-May for most US zones). Mulching too early traps cold and slows perennial regrowth.
Skip the table — use the calculator
Enter your real bed shape (circle, L, ring) and depth.
Open mulch calculator