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Mulch Calculator
Find how many cubic yards — and bags — of mulch your beds need.
How to use this calculator
Measure your bed's length and width in feet and decide how deep you want the mulch in inches, then enter all three and press Calculate. The tool returns the volume you need in cubic yards (how bulk mulch is sold and delivered) and the equivalent number of standard 2-cubic-foot bags. For an irregular bed, split it into rectangles, run each one, and add the results. Buying about 5–10% extra is wise to allow for settling and uneven ground.
The formula explained
Mulch volume is area times depth, converted to cubic yards:
cubic yards = (length × width × depth_inches ÷ 12) ÷ 27
Length times width gives the area in square feet. Dividing the depth in inches by 12 turns it into feet, so area times that depth gives cubic feet. Because bulk mulch is sold by the cubic yard, and one cubic yard is 27 cubic feet, dividing by 27 gives the yards. To count bags instead, divide the cubic feet by the bag size — most bagged mulch is 2 cubic feet.
A worked example
For a 20 ft × 5 ft bed at 3 inches deep: the area is 100 sq ft, the depth is 0.25 ft, so the volume is 25 cubic feet. That is 0.93 cubic yards, or about 13 bags of 2-cubic-foot mulch. Rounding up, you would order one cubic yard or buy 13–14 bags.
Frequently asked questions
How much mulch do I need?
Multiply bed area in square feet by depth in feet, then divide by 27 for cubic yards. This tool does it for you.
How deep should mulch be?
Two to three inches suits most garden beds — enough to block weeds and hold moisture without smothering plants.
How many bags in a cubic yard?
A cubic yard is 27 cubic feet, roughly 13.5 standard 2-cubic-foot bags.