Landscaping and garden

Mulch Calculator

Enter your bed size and depth to get cubic yards, cubic feet and the number of bags to buy. Includes a top-up option for beds that already have mulch.

Units
ft
ft
in
2 to 3 inches is enough in most beds.
cu ft
Check the bag: sizes vary by brand.

Enter your bed size and depth, then press Calculate.

How we calculate

Mulch is bought by volume: loose in cubic yards, or in bags labeled in cubic feet. We multiply the bed area by the depth, then convert.

Area: rectangle = length x width; circle = 3.14159 x (diameter / 2)^2 Volume (cu ft) = area (sq ft) x depth (in) / 12 Cubic yards = cubic feet / 27 Bags = cubic feet / bag size (cu ft), rounded up

Metric: meters and centimeters are converted with 1 ft = 0.3048 m, and bag sizes in liters with 1 cu ft = 28.32 liters.

How deep should mulch be?

Michigan State University Extension says “2 to 3 inches of mulch is adequate to get the maximum mulch benefit in most cases”, and if a bed already has mulch from last year, “a thin, 1-inch top-dressing is more than adequate”. Source: Michigan State University Extension, Mulching landscape beds FAQs.

Mississippi State University Extension lists 2 to 3 inches for pine or hardwood bark and 2 to 4 inches for shredded wood, says bulk mulch is sold in cubic yards, and advises pulling mulch back about 2 to 3 inches from tree and shrub trunks. Source: Mississippi State University Extension Service Publication 2301 (PDF).

Deeper is not better

Clemson University Cooperative Extension says fine-textured wood and bark mulches should not be more than 2 to 3 inches deep, because “excessive amounts of these fine-textured mulches can suffocate plant roots, resulting in yellowing of the leaves and poor growth.” Source: Clemson University Cooperative Extension, HGIC factsheet 1604: Mulch.

Check what is already in the bed before you buy. If the old layer is still 2 to 3 inches deep, you may only need to rake it and add a thin top layer.

Worked example

A 5 x 20 ft bed at 3 inches deep, using 2 cu ft bags:

  1. Area: 5 x 20 = 100 sq ft
  2. Volume: 100 x 3 / 12 = 25 cu ft
  3. Cubic yards: 25 / 27 = 0.93 cu yd
  4. Bags: 25 / 2 = 12.5, rounded up to 13 bags

A tree ring 10 ft across at 2 inches, using 3 cu ft bags: area = 78.54 sq ft, volume = 13.09 cu ft (0.48 cu yd), so 5 bags.

Cross-section of a garden bed with a 2 to 3 inch mulch layer pulled back from a shrub stemMulch 2 to 3 inSoilKeep mulch 2 to 3 in awayfrom stems and trunks
Spread mulch evenly, but pull it back from stems and tree trunks.

Bags or bulk?

Bags are handy for small beds and for carrying to the back yard. For larger areas, compare the bag count with a bulk price per cubic yard from a local garden center or landscape supplier; the calculator gives you both numbers so you can ask for a quote.

Mulching checklist

  • Pull weeds before you mulch
  • Measure each bed; add them up or use the square footage calculator for odd shapes
  • Check the depth of any old mulch before buying more
  • Keep mulch 2 to 3 inches away from stems and trunks
  • Wheelbarrow, garden fork or shovel, rake and gloves

FAQ

How much area does a cubic yard of mulch cover?

At 3 inches deep, one cubic yard (27 cu ft) covers 27 x 12 / 3 = 108 square feet. At 2 inches it covers 162 square feet.

How many bags of mulch are in a cubic yard?

It depends on the bag. A cubic yard is 27 cubic feet, so it equals 13.5 bags of 2 cu ft, or 9 bags of 3 cu ft.

Should I remove old mulch first?

Not always. Check the depth. If the old layer is still around 2 to 3 inches, Michigan State University Extension says a thin 1 inch top-dressing is more than adequate. Check the top-up box to calculate that.

Can I pile mulch around a tree trunk?

No. Mississippi State University Extension advises pulling mulch back about 2 to 3 inches from trunks.

Can I use metric units?

Yes. Switch to Metric to enter meters and centimeters, and enter the bag size in liters.

Part of our outdoor-career toolkit: From office to outdoors.

Estimates only. Results are estimates based on the measurements you enter. Check local building codes and your product labels, confirm quantities with your supplier, and buy a little extra material. This is not professional or structural advice. Last checked: September 27, 2026.

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