Yards for the truck or bags for the trunk — how much mulch your beds actually need, at the depth that actually stops weeds.
3 inches is the sweet spot. Under 2 inches, sunlight gets through and weeds laugh at you. Over 4 inches, water and air struggle to reach the soil and roots can suffocate. That's why 3" is the default here — 2" is only for topping up beds that already have mulch.
Please don't build a "mulch volcano" — that cone of mulch piled against a tree trunk. It traps moisture against the bark, invites rot and rodents, and slowly kills the tree. Keep mulch 2–3 inches away from trunks and stems, like a donut, not a volcano.
Bulk or bags? One cubic yard equals 13.5 two-cu-ft bags. Past 2–3 yards, bulk delivery is usually much cheaper per yard — bags win for small beds, tight access, or when your car is the delivery truck. Buy one bag extra; beds are never as rectangular as the tape measure claims.
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Mulch is sold by the cubic yard (bulk) or in 2-cubic-foot bags. The math starts from area and depth: one cubic yard covers 324 square feet at 1 inch deep, so cubic yards = square feet × depth-in-inches ÷ 324. For weed control and moisture, 2–3 inches is the sweet spot — thinner lets weeds through, much thicker can suffocate roots.
A 300-square-foot bed at 3 inches deep needs 300 × 3 ÷ 324 = about 2.8 cubic yards. In bags, since a cubic yard is 13.5 bags of 2 cubic feet, that's roughly 38 bags. At that size, bulk delivery is usually cheaper and a lot less hauling than three dozen bags — bags make sense mainly for small beds or touch-ups.
How deep should mulch be?
2–3 inches for most beds. Go too thin and weeds win; pile it too deep against stems and you invite rot.
Bulk or bags?
Bulk (by the yard) is cheaper for anything over roughly a cubic yard; bags are convenient for small areas and easy to carry.
How often do I re-mulch?
Most organic mulch breaks down over a year or two, so an annual top-up of an inch or so keeps depth and appearance up.