Mulch Calculator
Find how much mulch you need in cubic feet, cubic yards, and bags for garden beds.
How to use
Enter bed length, width, and depth, set waste, confirm bag volume from packaging, then calculate.
How the calculation works
Bed length, width, and depth become a volume. Waste is applied, then bag count uses the bag volume you enter.
Formula
volume_ft³ = length_ft × width_ft × depth_ft; volume_yd³ = volume_ft³ ÷ 27; adjusted = volume × (1 + waste%/100); bags = ceil(adjusted_ft³ ÷ bag_volume_ft³)
Example calculation
A 20 ft × 4 ft bed at 3 in deep is 20 ft³ (about 0.74 yd³) before waste.
Assumptions
Bed shape
Simple rectangle
Material: mulch · Key: geometry
For curved beds, approximate with rectangles or average width.
Source: Geometric model
Default bag volume (ft³ / bag)
2 ft³ per bag
Material: mulch · Key: bag_yield
Common retail bag size in US home centers; verify packaging.
Source: Planning default — confirm with your product label or supplier quote. Not a lab or manufacturer certification.
Settling / compaction
Not fully modeled
Material: mulch · Key: compaction
Fresh mulch can settle; depth is the target installed depth you enter.
Source: Model limitation
Practical notes
- Bulk mulch is often cheaper for larger beds.
- Avoid piling mulch against tree trunks (volcano mulching).
- Replenish depth as mulch decomposes over a season.
Limitations
- Does not calculate odd-shaped beds precisely.
- Bag sizes vary — always check packaging.
- Planning estimate only.
FAQ
- How deep should mulch be?
- Many beds use about 2–3 inches. Follow guidance for your plants and mulch type.
- Cubic yards or bags?
- Small beds are often bagged; larger areas are usually ordered in cubic yards.
Related calculators
Results are planning estimates. See the Calculator Disclaimer.