How much mulch do I need?

Bulk or bags — buying mulch the smart way

Mulch is sold two ways. Bagged mulch, usually in 2 cubic foot bags, is convenient for a bed or two. Bulk mulch, sold by the cubic yard and delivered in a pile, is much cheaper per unit once you need more than about ten bags. This calculator gives you both so you can see where the crossover is for your project.

The volume is length × width × depth. Because depth is in inches and the bed is in feet, divide the depth by 12 first, then divide the total by 27 to reach cubic yards. One cubic yard equals about 13.5 of those 2 cubic foot bags — so if the tool says two yards, that's roughly 27 bags, and a bulk delivery starts making sense.

Aim for a 2–3 inch layer. Thinner and weeds push through; much thicker and you can starve roots of water and air. Refresh the top inch each season rather than piling on a whole new layer every year.

A worked example: two beds, one order

Most yards have more than one bed. Say you have a 30 × 4 foot strip along the front of the house and a 12 × 6 foot bed by the mailbox, both getting 3 inches. Add the areas first: 120 + 72 = 192 ft². At 3 inches deep that is 192 × 0.25 = 48 cubic feet, or 1.78 cubic yards, or 24 bags of 2 ft³.

You can enter each bed separately and add the results, or enter one bed with the combined area (for example 192 × 1 ft). Either way gives the same volume, because mulch is only area times depth.

How far one cubic yard goes

One cubic yard is 27 cubic feet, so it equals 13.5 bags of 2 ft³. That is the number to compare when a garden center quotes bags against a landscape yard quoting bulk.

Mistakes that waste mulch (and plants)

• Piling it against trunks. "Volcano" mulching traps moisture against the bark and invites rot and rodents. Keep mulch 3 to 6 inches away from tree trunks and the base of shrubs.
• Adding a full layer every year. Mulch breaks down slowly. If last year's layer is still 2 inches deep, top it up by an inch, not three. The calculator works for top-ups too: enter 1 inch as the depth.
• Forgetting that fresh mulch settles. Shredded hardwood fluffs up when it is spread and settles over the first few weeks, so 3 inches put down ends up closer to 2½.
• Mulching over weeds. Pull or smother established weeds first. Mulch stops new seeds sprouting; it does not stop perennial weeds that are already rooted.

What it costs

Bagged mulch typically costs $3 to $6 per 2 ft³ bag in the US, depending on the type, and dyed mulch sits at the top of that range. Bulk mulch from a landscape supplier usually runs $30 to $50 per cubic yard, plus a delivery fee that is often $40 to $100. For the example above, 24 bags at around $4 come to about $96, while 2 yards of bulk run roughly $60 to $100 plus delivery. Above about two yards, bulk almost always wins. Check local prices; they swing a lot by region and season.