How Much Mulch Do I Need? (Yards, Bags & Depth Guide)

"How much mulch do I need?" is the question I hear every spring. And every spring, I watch neighbors make the same two mistakes: buying 5 bags for a job that needs 30, or ordering 4 yards for beds that need 1.5.

Let's get you the right number in about 60 seconds.

The short answer

Measure your beds (length × width in feet), pick a depth (3 inches is standard), and use this:

Cubic yards = Length × Width × (Depth ÷ 12) ÷ 27

That's it. Everything below is just making this painless.

Step by step with a real example

Say you've got a bed that's 25 ft long × 5 ft wide, and you want the standard 3 inches:

1. Convert depth: 3 ÷ 12 = 0.25 ft
2. Cubic feet: 25 × 5 × 0.25 = 31.25 cu ft
3. Cubic yards: 31.25 ÷ 27 = 1.16 cu yd → order 1.5 yards (they sell in halves)

In bags: 1.16 × 13.5 = 16 bags (2 cu ft bags)

How deep should it go?

This is where most people go wrong:

• 3 inches — the answer 90% of the time. Blocks weeds, holds moisture, looks great.
• 2 inches — fine for topping up last year's mulch that's just faded.
• 4 inches — only for brand-new beds over bare soil with aggressive weeds.
• Less than 2 inches — honestly, don't bother. Weeds will push right through.

And please — keep it 3 inches away from tree trunks and house siding. Mulch piled against bark rots the tree (the infamous "mulch volcano"), and mulch against siding is a termite invitation. I see both on every street in America.

Bags vs. bulk — the money math

| Amount needed | Bags (2 cu ft) | Bulk | Winner | |---|---|---|---| | Under 1 yard | ~13 bags | 1 yd delivered | Bags (no delivery fee) | | 1–2 yards | 14–27 bags | $40–80/yd | Toss-up | | 2+ yards | 27+ bags | $40–80/yd | Bulk, easily |

Real numbers: a 2 cu ft bag runs $3–5 at the big box stores. A bulk yard (13.5 bags' worth) delivered is often $40–70. Do the math — bulk is usually half the price once you're past 2 yards. Plus they dump it in your driveway and you skip 30 trips with a trunk full of bags.

My rule: under a yard, bags. Over two, bulk. Between? However much you hate loading bags into your car.

Don't forget settling

Fresh mulch settles 10–20% in the first month. If you want a finished 3-inch bed, lay about 3.5 inches fresh. Then fluff it with a rake after a few weeks. Don't over-order to compensate — you'll just end up with a mountain.

Quick reference (3" depth)

| Bed size | Cubic yards | 2 cu ft bags | |---|---|---| | 10 × 4 ft | 0.37 | 5 | | 15 × 5 ft | 0.69 | 10 | | 25 × 5 ft | 1.16 | 16 | | 30 × 8 ft | 2.22 | 30 (bulk!) | | 50 × 10 ft | 4.63 | 63 (bulk!) |

One more thing — measure every bed separately and add them up. Eyeballing "eh, probably 2 yards" is how you end up making a second trip. Ask me how I know. (Twice. Two springs in a row.)

Too lazy for the math? Our free mulch calculator gives you yards, bags, and cost in ten seconds flat.