Mulch math is one multiplication and two divisions — but garden centers sell in three units (bags, cubic feet, cubic yards), so this calculator answers in all of them at once, plus the cost.
The worked example
A 200 sq ft bed at the standard 3-inch depth: 200 × 3 ÷ 12 = 50 cubic feet = 1.85 cubic yards = 25 two-cubic-foot bags. At $4 a bag that's $100 — a bulk yard delivered often runs cheaper, which is why the calculator nudges you toward bulk quotes past one yard.
Depth: the variable that matters
2–3 inches suppresses weeds and holds moisture; deeper suffocates roots and invites rot. Topsoil for new beds runs 4–6 inches; compost top-dressing just 1–2 — same math, different slider position. And keep mulch pulled back from trunks: the infamous "mulch volcano" shortens tree lives.
Bags vs bulk: the 27 rule
A cubic yard is 27 cubic feet — 13.5 standard bags. Hauling 14 bags is a workout; a bulk drop is one wheelbarrow-day. Price crossover typically lands right around 1 yard, so the yard figure doubles as your buy-signal.
Irregular beds and companions
For odd shapes, break the bed into rectangles and sum the areas — the square footage calculator handles the pieces. Gravel and stone (sold by weight, not just volume) get their own density math in the gravel calculator, and slab pours belong to the concrete calculator.
Coverage estimates; settle 10–15% extra for fluffy materials.