Mulch Calculator
Enter your bed size and depth to get cubic yards, bag count, and whether bags or bulk delivery is cheaper.
The short answer
Formula. Cubic feet = bed length × width × (depth in inches ÷ 12); bags = cubic feet ÷ bag size, rounded up to a whole bag.
Example. A 10 ft × 12 ft bed mulched 3 in deep holds 30 cubic feet — fifteen 2-cubic-foot bags, or about 1.1 cubic yards in bulk.
How this calculator works
Mulch math is pure volume. Take your bed's square footage (length × width, or the sum of odd sections), multiply by the depth in feet — inches ÷ 12 — and you have cubic feet. A 10 × 12 ft bed at 3 inches deep is 10 × 12 × 0.25 = 30 cubic feet. Divide by 27 and that is 1.11 cubic yards, the unit bulk suppliers sell by. Bagged mulch is sold by the bag at 2 cubic feet (the standard at big-box stores) or 3 cubic feet, so the same 30 cubic feet is 15 of the 2-cu-ft bags or 10 of the 3-cu-ft ones — the calculator rounds up because stores will not sell you a fraction of a bag.
The conversion worth memorizing: one cubic yard = 13.5 bags of 2 cubic feet (or 9 of the 3-cubic-foot size). Bulk mulch delivered by the yard is almost always cheaper per unit above roughly two yards — bagged product typically costs two to three times as much, and you carry it twice — but most bulk yards have a delivery minimum and charge a drop fee, which is why small jobs still end up in bags. Enter both prices above and the comparison lines appear.
Depth is where people waste money. Mulch is not better the deeper it is: 2 to 3 inches over established beds holds moisture and blocks weeds, while 6 inches invites rot at the trunk and voles in the lawn edge. If old mulch is matted but still breaking down, fluff it instead of stacking new on top — and never let mulch touch tree bark; keep a few inches of clear air around trunks and crowns, the classic "mulch volcano" mistake kills trees slowly.
Sources & review date
- Bag sizes (2 and 3 cubic feet) are the standard US retail mulch bag sizes; bulk mulch is sold by the cubic yard.
Last reviewed: October 2026. Numbers that drift (fees, prices, densities) are editable inputs on this page.
Mulch FAQs
How many 2 cu ft bags of mulch do I need for 100 sq ft?
At 3 inches deep, 100 sq ft is 25 cubic feet — 13 bags of 2 cubic feet (12.5 rounded up). At 2 inches it is 17 bags' worth of volume, about 16.7 cubic feet, so 17 bags.
How much does a yard of mulch cover?
One cubic yard covers 324 sq ft at 1 inch, 162 sq ft at 2 inches, or about 108 sq ft at 3 inches. That last number is the practical default: a yard does a 10 × 11 ft bed at the standard depth.
How many cubic yards will my pickup truck hold?
A full-size 8-ft bed holds roughly 2 to 3 cubic yards of mulch level to the rails (a compact bed, about 1.5). Beyond that, delivery is usually cheaper than a second trip once fuel and your back are counted.
Should I mulch in spring or fall?
Spring, after the soil warms, is the main season — that is when demand and prices peak. A fall top-up protects shallow roots and heaving plants through freeze-thaw. Either way, the volume math does not change.