Mulch Calculator

Calculate how much mulch you need for a garden bed. Enter bed dimensions and depth to get cubic feet, cubic yards, and bag count.

ft

Length of the garden bed.

ft

Width of the garden bed.

in

Standard: 3". Annual top-dressing: 2". Weed suppression: 4". Playground: 6".

cu ft

Cubic feet per bag. Common: 2 cu ft (Home Depot), 1.5 cu ft (premium), 3 cu ft (bulk).

%

Extra for settling, uneven ground. Default 5%.

How this calculator works

This mulch calculator estimates volume in three steps:

  1. Volume in cubic feet: bed length × bed width × (depth / 12) — converting inches to feet.
  2. Cubic yards: cubic feet / 27 — the unit for bulk mulch delivery.
  3. Bags: if you enter bag size (default 2 cu ft), the calculator divides total volume by bag size and rounds up.

The waste allowance (default 5%) covers settling, uneven ground, and minor spreading variations.

Formula

volume_cuft = bed_length × bed_width × (depth / 12)
volume_cuyd = volume_cuft / 27
volume_with_waste = volume_cuft × (1 + waste_pct / 100)
bags = ceil(volume_with_waste / bag_size)  [if bag_size > 0]

Example

For a 10 × 5 ft bed at 3" depth, 2 cu ft bags, 5% waste:

  • volume_cuft = 10 × 5 × (3/12) = 12.5 cu ft
  • volume_cuyd = 12.5 / 27 = 0.463 cu yd
  • volume_with_waste = 12.5 × 1.05 = 13.13 cu ft
  • bags = ceil(13.13 / 2) = 7 bags

Important assumptions

  • Standard mulch depth: 3" for new beds, 2" for annual top-dressing. Avoid >4" around plant stems.
  • Default bag size: 2 cu ft (most common at Home Depot/Lowes). Premium hardwood: 1.5 cu ft. Bulk bags: 3 cu ft.
  • Bulk mulch is sold by the cubic yard (1 cu yd = 27 cu ft). For large beds, bulk delivery is cheaper than bagged.
  • One 2 cu ft bag covers ~8 sq ft at 3" depth. One cubic yard covers ~108 sq ft at 3" depth.
  • Waste 5% covers settling and uneven ground — not enough for significant slope or irregular shapes.

FAQ

How much mulch do I need for a 10×10 bed?
A 10×10 bed at 3" depth needs 25 cu ft of mulch (0.93 cu yd). With 5% waste: 26.25 cu ft → 14 bags (at 2 cu ft/bag) or 1 cu yd bulk.
How deep should mulch be?
3 inches for new beds, 2 inches for annual top-dressing. Avoid >4 inches around plant stems — too much mulch can rot the stems. For playgrounds, use 6+ inches of playground mulch.
How many bags of mulch equal one cubic yard?
One cubic yard = 27 cu ft. At 2 cu ft per bag, that's 13.5 → 14 bags. At 1.5 cu ft per bag, that's 18 bags. For large beds, bulk delivery by the cubic yard is much cheaper.
How much does a bag of mulch cover?
A 2 cu ft bag covers approximately 8 sq ft at 3" depth, or 12 sq ft at 2" depth. A 1.5 cu ft bag covers 6 sq ft at 3" depth.
Should I buy bagged or bulk mulch?
For beds under 2 cubic yards (27 bags at 2 cu ft), bagged is convenient. For larger beds, bulk delivery by the cubic yard is typically 40-60% cheaper. Most suppliers have a 1-2 cubic yard minimum for delivery.