Mulch Calculator
Cubic yards or bags of mulch for garden beds and borders.
3 in for new beds, 1 to 2 in for a refresh.
You need
0.74 cubic yards
Bulk delivery is usually cheaper above about 2 cubic yards.
- 2 cu ft bags
- 10 bags
- 3 cu ft bags
- 7 bags
- Bed area
- 80 sq ft
Estimates only. Verify quantities before ordering.
How this is calculated
Volume = length (ft) x width (ft) x depth (in) / 12, then divided by 27 for cubic yards. One cubic yard equals 13.5 bags at 2 cu ft or 9 bags at 3 cu ft.
Measure the bed's length and width in feet, pick a depth, and this calculator gives you the volume in cubic yards for bulk orders plus the equivalent number of bags. For irregular beds, break the shape into rough rectangles, run each one, and add the results together.
Depth is the main decision. A fresh bed benefits from a full 3 inches, which suppresses weeds and holds moisture well. An annual refresh over existing mulch usually only needs 1 to 2 inches. More than 4 inches is counterproductive, since thick mulch can suffocate roots and hold too much moisture against stems.
Mulch for common bed sizes
Rows use a full 3 inch depth for new beds except where noted. One cubic yard equals 13.5 of the common 2 cu ft bags.
| Bed size | Cubic yards | 2 cu ft bags |
|---|---|---|
| 4 x 10 ft, 3 in | 0.37 cubic yards | 5 bags |
| 4 x 25 ft, 3 in (long border) | 0.93 cubic yards | 13 bags |
| 10 x 10 ft, 3 in | 0.93 cubic yards | 13 bags |
| 20 x 4 ft, 2 in (refresh) | 0.49 cubic yards | 7 bags |
| 20 x 10 ft, 3 in | 1.85 cubic yards | 25 bags |
| 30 x 15 ft, 3 in (full yard) | 4.17 cubic yards | 57 bags |
Mulch types and how long each lasts
Shredded hardwood is the most common bulk mulch, knits together so it stays put on slopes, and breaks down over a season or two into the soil, which is a benefit if you want the organic matter and a cost if you dislike topping up. Bark nuggets last longer and float away in heavy rain, making them a poor choice on any grade or near a downspout.
Cedar and cypress resist decay and hold their appearance longer, with cedar carrying a scent that deters some insects. Pine straw is light, excellent on slopes because it mats, and favored for acid-loving plantings. Dyed mulches are usually recycled wood carrying a colorant; the dye itself is generally harmless, though the underlying wood quality varies far more than the color suggests.
Rubber mulch does not decompose and is sometimes chosen for playgrounds, but it adds nothing to the soil, holds heat, and is effectively permanent, which becomes a problem the first time you want to replant the bed. For ornamental beds, an organic mulch that breaks down is usually the better long-term choice.
Depth, and the mistake that kills trees
Two to three inches is the working range for most beds. Below about 2 inches, sunlight reaches the soil and weeds germinate, which defeats the main practical purpose. Beyond 4 inches, mulch begins to shed water rather than let it through and can keep the soil beneath waterlogged and oxygen starved, which harms shallow roots.
Never pile mulch against a trunk. The volcano of mulch heaped around street trees keeps the bark permanently damp, invites rot and rodents, and encourages roots to grow into the mulch instead of the soil. Pull mulch back to leave a few inches of clear ground around every trunk and the root flare visible. This single detail causes more slow tree decline in landscaped yards than almost anything else.
Topping up versus replacing
Because organic mulch decomposes from the bottom, the usual maintenance is topping up rather than replacing. Measure the existing depth before ordering: a bed that still holds 2 inches needs only an inch to refresh it, which is half the material of a full application. Fluffing the existing layer with a rake often restores much of the appearance without buying anything at all.
Occasionally a full replacement is warranted. If the old mulch has matted into a water-shedding crust, developed a persistent sour smell from anaerobic storage, or accumulated well past 4 inches from years of topping up, strip it back before adding more. Otherwise you are steadily raising the grade around your plantings, which buries root flares and creates the same problem as piling mulch against a trunk.
Common questions
How many bags of mulch are in a cubic yard?
A cubic yard is 27 cubic feet, so it equals 13.5 of the common 2 cu ft bags or 9 of the 3 cu ft bags. If you need more than about 25 bags, price out a bulk delivery: it is almost always cheaper per yard and saves a lot of lifting.
How deep should mulch be?
2 to 3 inches is the sweet spot for most beds: enough to block light from weed seeds and slow evaporation without smothering plant roots. Coarse mulches like bark nuggets can go slightly deeper, and fine mulches like shredded leaves should stay closer to 2 inches.
Should mulch touch tree trunks and plant stems?
No. Pull mulch 2 to 3 inches back from trunks and stems. Piling mulch against bark (the so-called mulch volcano) traps moisture, invites rot and pests, and encourages girdling roots. The mulch ring should look like a donut, not a volcano.
How often does mulch need to be replaced?
Organic mulches break down over one to two seasons. Most beds do well with a 1 to 2 inch top-up each spring. Rake and fluff the old layer first, and only remove it if it has compacted into a water-shedding mat.