How to use this calculator
- Measure the bed. Length and width in feet — round shapes can be approximated as rectangles.
- Choose depth. Most beds use 2–3 inches; tree rings 3–4 inches.
- Pick bag size. Default is 2 ft³ (most retail bags). Bulk delivery is by cubic yard.
- Read result. You get cubic yards for bulk delivery and exact bag counts for retail buying.
Formula
Volume (yd³) = Length × Width × Depth ÷ 27
Worked example
A 20 ft × 6 ft bed at 3 inches deep equals 1.11 cubic yards (30 cubic feet). That's 15 bags of 2 ft³ mulch or 10 bags of 3 ft³ mulch.
Tips for accurate results
- A 2-inch layer is the minimum for weed suppression.
- Don't pile mulch against tree trunks — leave a 2-inch gap.
- Bulk delivery is typically cheaper than bags above 2 yd³.
- Refresh every spring; replace fully every 2–3 years.