How to Calculate How Much Mulch You Need

Mulch suppresses weeds, retains moisture, regulates soil temperature, and improves curb appeal. The key is applying the right depthβ€”too little and it won't work; too much and you can suffocate plant roots.

The Formula

Cubic Yards = (Length Γ— Width Γ— Depth in feet) / 27

Or using inches for depth:

Cubic Yards = (Square Footage Γ— Depth in inches) / 324

Step-by-Step Example

Flower bed: 20 ft Γ— 8 ft = 160 sq ft Desired depth: 3 inches

Cubic yards = (160 Γ— 3) / 324 = 480 / 324 = 1.48 cubic yards

Recommended Mulch Depths

PurposeDepth
Weed suppression3–4 inches
Moisture retention2–3 inches
Around trees2–3 inches (keep away from trunk)
Annual refresh1–2 inches (top up over existing mulch)

Converting Between Units

  • 1 cubic yard = 27 cubic feet
  • 1 cubic foot = approximately 2 standard bags (2 cubic feet per bag)
  • 1 cubic yard β‰ˆ 13–14 bags (2 cubic feet each)

For the example above: 1.48 yards Γ— 13.5 bags/yard β‰ˆ 20 bags

Buying in Bulk vs. Bags

  • Bags: Convenient for small areas, easy to transport
  • Bulk delivery: More economical for areas over 3–4 cubic yards (>$50 savings typical)

Use our mulch calculator for any garden bed size and desired depth.