Mulch Calculator — Cubic Yards & Bags
Too little mulch and weeds win; too much and roots suffocate. Enter your bed for exact cubic yards and bag counts at the ideal 3" depth. Free, instant, no signup.
Quick answer
Multiply length × width × depth (all in feet) and divide by 27 for cubic yards. A 20×10 ft bed at 3 inches deep needs about 1.85 cubic yards (25 two-cu-ft bags). One cubic yard equals 13.5 bags.
3" is the sweet spot — enough to block weeds, not so deep it suffocates roots. Refresh beds yearly.
Your mulch estimate
Mulch needed
1.85
cubic yards
- Volume
- 50.0 cu ft
- 2-cu-ft bags
- 25
Bulk yards are cheaper than bags for big beds; bags win for small touch-ups.
How the calculation works
- Volume in cubic feet: length × width × (depth in inches ÷ 12). A 20×10 ft bed at 3" = 50 cu ft.
- Cubic yards: cubic feet ÷ 27. Bulk mulch is sold by the yard — round up to the nearest half yard.
- Bags: cubic feet ÷ 2 (standard bag size), rounded up. One yard = 13.5 two-cu-ft bags.
Mulch depth guide
| Depth | When to use it |
|---|---|
| 2" | Annual refresh over existing mulch |
| 3" | The standard — new beds and yearly top-ups |
| 4" | Maximum for aggressive weed pressure |
| 6"+ | Never around plants — suffocates roots |
Tips from the pros
- Keep mulch off stems and trunks. The dreaded "mulch volcano" rots bark — leave a few inches clear.
- Water after spreading. It settles the mulch and starts moisture retention immediately.
- Buy bulk at 3+ yards. Delivery fees sting on small loads but vanish per-yard on big ones.
- Edge your beds first. A clean spade edge keeps mulch where it belongs after every rain.
- Refresh, don't replace. Old mulch becomes compost — top it up yearly instead of stripping it.
Common questions
Multiply bed length × width × depth (in feet) for cubic feet, then divide by 27 for cubic yards. Example: a 20×10 ft bed at 3" deep = 20 × 10 × 0.25 = 50 cu ft = 1.85 cubic yards. Order 2 yards.