Mulch in bulk is measured by the inconvenient and non-intuitive square yard. Since most of us compute garden or yard area in feet, it’s a challenge to figure out how much mulch to buy.
Turns out, there’s a simple formula for figuring this out:
Area to be covered (in square feet) x depth of mulch (in inches) divided by 324 = square yards (or fraction thereof) of mulch*
Why 324? Because that’s the amount of mulch, spread to a thickness of 1 inch, in a square yard (3 x 3 x 3 x 12).
Picture a 3 x 3 x 3 foot cube (square yard) of mulch, cut into layers 1 inch thick. You would have 36 (3 feet x 12 inches/foot) layers, each 1 inch thick, 3 feet wide and 3 feet long.
Or: 3 feet wide x 3 feet long x 36 layers = 324 square feet to a depth of 1 inch = 1 square yard to a depth of 1 inch
By the way, the conversion formulas are similar if you’re buying your mulch in other units, like 2 square foot bags (in that case, divide by 24) or 3 square foot bags (divide by 36).
Anyhow, as you can see, a square yard is a helluva lot of mulch.
That’s why, when a co-worker tells you Monday morning that s/he spread 5 yards of it over the weekend, the proper response is admiration and awe.
*Use 22/7 x radius(in feet) x radius(in feet) to compute a circular area.