Mulch calculator
Enter the size of your bed and how deep you want the mulch — get cubic yards, bag counts and an optional cost estimate instantly. Everything calculates in your browser.
Mulch needed
How much mulch do I need?
Mulch math has three steps: find the area of your bed, multiply by your depth to get volume, then convert that volume into yards or bags.
Worked example: a 20 ft × 4 ft border mulched 3 inches deep is 80 ft² × 3 ÷ 12 = 20 ft³ ≈ 0.74 yd³ — that's ten 2 ft³ bags (0.74 yd³ rounds up to about 10 bags) plus a little waste, so call it a half-yard scoop or 11 bags.
How deep should mulch be?
Most extension services recommend 2–4 inches of mulch over garden soil. Thinner than 2 inches lets weeds through; deeper than 4 inches can suffocate roots and trap moisture against bark. Around trees, keep mulch 3–6 inches off the trunk — no “volcanoes”.
| Purpose | Typical depth | 1 yd³ covers |
|---|---|---|
| Annual top-up in existing beds | 1–2 in | 162–324 ft² |
| Standard garden bed | 2–3 in | 108–162 ft² |
| New bed, first mulch over bare soil | 3–4 in | 81–108 ft² |
Bag sizes and bulk equivalents
The standard US mulch bag holds 2 cubic feet (some sell 3 ft³). Bulk mulch is sold by the cubic yard = 27 ft³. That means:
- 13.5 two-cubic-foot bags = 1 cubic yard
- 9 three-cubic-foot bags = 1 cubic yard
- A standard short-bed pickup (6 ft bed) holds roughly 2–3 yd³ level
Bulk is almost always cheaper once you need more than about a dozen bags — see our bags vs yards comparison and the full mulch coverage chart.
How much does mulch weigh?
Shredded bark and wood-chip mulch weigh about 400–550 lb per cubic yard depending on moisture and grind (the calculator uses 450 lb/yd³, about 0.23 short tons). Wet mulch can be a third heavier — worth knowing if you're hauling it in a trailer.