Mulch Calculator

Please enter length, width and depth greater than 0.
–cubic yards
–cubic feet
–2 cu ft bags
–3 cu ft bags

Estimate only. Bag sizes vary by brand, so check the label.

How to use this calculator

Measure the bed length and width in feet, enter the depth you want in inches, and press Calculate. You get cubic yards for bulk delivery and the number of 2 and 3 cubic foot bags.

The formula

Cubic feet = length (ft) × width (ft) × depth (in) ÷ 12
Cubic yards = cubic feet ÷ 27

Example: A 20 ft × 5 ft bed at 3 inches deep is 25 cubic feet, or 0.93 cubic yards. With 10% extra you need about 1.02 cubic yards.

What affects how much mulch you need

The calculator turns the size and depth of your bed into cubic yards, cubic feet and bags. Depth is the biggest factor. Doubling the depth doubles the mulch, so it is worth choosing the depth carefully before you buy.

Choose the right depth

  • New beds: About 3 inches is a good target for weed control and moisture.
  • Topping up: If old mulch is still in place, 1 to 2 inches is often enough.
  • Around trees: About 3 to 4 inches, spread wide but kept a few inches from the trunk.
  • Fine mulch: Shredded or fine mulch packs down, so a slightly thinner layer often works.

Worked examples

The 20 ft by 5 ft bed from the formula above needs 25 cubic feet at 3 inches deep. Before adding extra, that is about 13 bags of 2 cubic feet or 9 bags of 3 cubic feet. If you only top it up with 1 inch, you need about 8.3 cubic feet, roughly a third as much.

A longer 30 ft by 4 ft border at 3 inches needs 30 cubic feet. That is about 1.11 cubic yards, or about 1.22 cubic yards with 10 percent extra. At a price of $40 per cubic yard, for example, bulk material would cost about $49 before delivery.

Bags or bulk

Bags are easy to carry and good for small beds. Bulk is usually cheaper per yard but often has a delivery fee and a minimum order. Compare the full cost, including delivery, before you decide. Enter your local price per cubic yard to see the total.

Tips for spreading

  • Weed and water the bed before you mulch.
  • Edge the bed first so mulch stays in place.
  • Dump small piles across the bed and spread with a rake rather than one big pile.
  • Pull mulch back from plant stems and the house foundation.

Common mistakes

  • Piling mulch against tree trunks, often called volcano mulching. It holds moisture against the bark and can invite rot and pests.
  • Adding a full new layer every year on top of the old one, which can smother roots over time.
  • Measuring depth in feet instead of inches.
  • Forgetting to measure curved or irregular beds as smaller rectangles and adding them up.

For odd shapes, split the bed into rectangles, run each one through the calculator and add the results together.

Frequently asked questions

How much does one cubic yard of mulch cover?
About 108 square feet at 3 inches deep, 162 square feet at 2 inches deep, or 81 square feet at 4 inches deep.
How deep should mulch be?
Use 2 to 3 inches for flower beds and around shrubs, and 3 to 4 inches around trees. Keep mulch a few inches away from trunks and stems.
How many 2 cubic foot bags make a cubic yard?
13.5 bags, so round up to 14.
Is bulk mulch cheaper than bags?
Usually yes. For more than about 3 cubic yards, bulk delivery is typically cheaper than bags.
Should I add extra for waste?
Adding 5 to 10 percent covers uneven ground and settling.
When is the best time to put down mulch?
Mid to late spring is a popular time, after the soil has warmed and spring weeds are pulled. Fall mulching also works well, since it protects roots through winter. Avoid mulching frozen or very wet soil, and pull mulch back from plants that need the sun to warm the ground.
Should I remove old mulch before adding new mulch?
Usually not. Old organic mulch breaks down and feeds the soil. Rake it to loosen any matted layer, then top it up to reach a total of about 2 to 3 inches. Remove it only if it is moldy, very deep or packed so tight that water cannot soak through.
What type of mulch is best for flower beds?
Shredded hardwood, pine bark and pine straw are common choices. They break down slowly and improve the soil. Fine shredded mulch stays in place on slopes. Rubber and stone mulch last longer but add no nutrients and can heat up the soil, so they suit paths better than planting beds.