Mulch Calculator

How it works

Mulch is a layer of material spread over a bed, so the amount you need is the area of the bed multiplied by how deep you want the layer. Length times width gives the area in square feet; multiplying by the depth in feet (inches divided by 12) gives the volume in cubic feet.

Bagged mulch is sold in 2 and 3 cubic foot bags, so the volume divided by the bag size is the number of bags. It is rounded up because a part bag still has to be bought. Bulk mulch is sold by the cubic yard, which is 27 cubic feet; use that figure to get a delivery quote and compare it with the cost of bags.

Formula

area        = length × width
cubic feet  = area × (depth ÷ 12)
cubic yards = cubic feet ÷ 27
bags        = cubic feet ÷ bag size, rounded up

Example

A 10 ft × 10 ft bed is 100 sq ft. Mulched 3 in deep, that is 100 × 3 ÷ 12 = 25 cu ft, or 25 ÷ 27 = 0.93 cu yd.

In 2 cu ft bags that is 25 ÷ 2 = 12.5 bags, so you would buy 13. In 3 cu ft bags it is 8.3, so 9.

Assumptions and limitations

• The bed is a rectangle. For an L-shaped bed or several beds, add the areas together and enter the total as the length with a width of 1.
• Mulch settles after it is spread. 3 in is the usual depth for suppressing weeds and holding moisture on a new bed; 2 in is enough to refresh a bed that already has mulch.
• Bag volumes are nominal. The contents of a "2 cu ft" bag can settle in the bag and look like less.
• Bulk suppliers usually sell by the half or whole cubic yard and round up. The cubic yard figure here is exact; expect to order the next half yard above it.
• No allowance is made for waste or spillage.

Frequently asked questions