Mulch Calculator
Work out how much mulch or topsoil a bed needs — length, width, and depth become cubic yards, plus a count of standard bags.
How it works
The volume is the bed's area times how deep you're spreading. Depth is in inches while the bed is in feet, so we divide the depth by 12 first — a 20-by-10 bed at 3 inches comes to about 50 cubic feet.
Bulk mulch and soil are sold by the cubic yard, and a yard is 27 cubic feet, so we divide by 27. That example bed works out to roughly 1.85 cubic yards for a delivery.
Prefer bags? The standard mulch bag holds 2 cubic feet, so we divide the volume by two and round up. Bagged is convenient for small beds; by the yard gets cheaper once you're covering real ground.
Frequently asked questions
How deep should I spread mulch?
Two to three inches is the sweet spot for most beds — enough to hold moisture and block weeds without smothering roots. Around trees, keep it off the trunk so you don't invite rot.
How many bags are in a cubic yard of mulch?
About 13 and a half of the standard 2-cubic-foot bags, since a yard is 27 cubic feet. Once you're past a handful of bags, a bulk delivery by the yard usually costs less per unit.
Does this work for topsoil or compost too?
It does. The volume math is the same whatever you're spreading — mulch, topsoil, or compost — so enter your bed size and depth and read off the cubic yards or bags either way.
Should I round up my order?
A little, yes. Beds are rarely perfect rectangles and settling eats some depth, so ordering slightly over means you finish the job instead of stopping one wheelbarrow short.