A cubic yard of mulch covers about 108 square feet at 3 inches deep, and takes 13.5 bags at the common 2-cubic-foot bag size. To size your own beds: area in square feet × depth in feet ÷ 27 for cubic yards.
Coverage per cubic yard
| Depth | Area covered | Bags (2 cu ft) for that area |
|---|---|---|
| 1 in | 324 sq ft | 13.5 |
| 2 in | 162 sq ft | 13.5 |
| 3 in | 108 sq ft | 13.5 |
| 4 in | 81 sq ft | 13.5 |
The bag count per cubic yard never changes — 27 cubic feet ÷ 2 = 13.5 bags — only the area it spreads over does.
| Bag size | Bags per cubic yard |
|---|---|
| 1.5 cu ft | 18 |
| 2 cu ft | 13.5 |
| 3 cu ft | 9 |
How deep should mulch be?
2–3 inches is right for most beds; 3–4 inches where you want real weed suppression. Deeper isn’t better — mulch piled past 4 inches holds water against roots and starves the soil of air.
| Situation | Depth |
|---|---|
| Annual and perennial beds | 2–3 in |
| Shrub beds, weed suppression | 3–4 in |
| Around trees (never touching bark) | 3–4 in |
| Refreshing last year’s mulch | 1–2 in |
| Fine mulch or compost | 2 in |
Two rules worth more than the depth number:
- Never volcano a tree. Mulch mounded against the trunk traps moisture against the bark and invites rot and rodents. Pull it back several inches to expose the root flare.
- Refresh, don’t rebuild. Existing beds usually need 1–2 inches topped up, not a full 3. Rake and fluff what’s there first; you may need less than you think.
Worked example
A 300 sq ft bed at 3 inches deep:
- Volume: 300 × 0.25 = 75 cubic feet
- Cubic yards: 75 ÷ 27 = 2.8 cubic yards
- Bags: 75 ÷ 2 = 38 bags at 2 cubic feet each
The Mulch Calculator gives cubic yards and bag count together, plus a bulk cost estimate if you have a price per yard.
Bulk or bagged?
The crossover is usually around 10–12 bags. Past that, bulk is cheaper per cubic yard even after the delivery fee — and you’re not breaking down 40 plastic bags.
| Bagged | Bulk | |
|---|---|---|
| Cost per cubic yard | Higher | Lower |
| Delivery | You haul it | Fee, often $50–100 |
| Handling | Easy, incremental | Needs a tarp or driveway space, and a wheelbarrow day |
| Leftovers | Store the bags | It’s a pile until you spread it |
| Best for | Small beds, touch-ups, no truck | Whole-yard mulching |
One practical note: a cubic yard of mulch weighs roughly 400–800 lb depending on type and moisture, so it will fit in a pickup where a yard of soil or gravel would not.
Choosing a mulch
- Shredded hardwood — knits together, stays put on slopes, breaks down into the soil.
- Bark nuggets — last longer, but float and wash out in heavy rain or on grades.
- Pine straw — light, good for acid-loving plants, needs topping up more often.
- Cedar / cypress — rot resistant, holds color longer, costs more.
- Dyed mulch — color fades in a season or two; the dye is cosmetic, not a preservative.
- Rubber mulch — doesn’t decompose, which also means it adds nothing to the soil.
Organic mulches all break down. That’s a feature — it’s how beds get their organic matter — but it’s why you’re topping up every year or two.
Run your bed dimensions through the Mulch Calculator to compare the bag count against a bulk delivery for the same area.