Calculator · Mulch
Mulch Calculator: How Many Bags or Yards of Mulch Do I Need?
Measure your beds or tree rings, pick the depth and the bag size, and get how many bags to buy or how many yards to order, with the cost of each. If the beds already have mulch, it only counts what you need to add.
Materials ticket · Mulch
Enter your measurements and your shopping list prints here.
How to calculate how much mulch you need
- Find the area in square feet. Length × width for a bed; 3.14 × radius² for a circle. Split curvy beds into rectangles and add them up.
- Decide how much to add. The depth you want minus what is already there. Push a trowel into the old mulch and measure the layer.
- Convert to bags or yards. Area × depth in inches ÷ 324 gives cubic yards. Multiply by 27 and divide by the bag size for bags.
Shortcut: a 2 cu. ft. bag covers 8 ft² at 3 inches. Divide your square footage by 8 and round up.
Mulch for common projects
Calculated with the same engine as the calculator, with undyed mulch at $30 a yard in bulk and 2 cu. ft. bags at $3.97. Bulk is rounded up to the quarter yard; delivery is not included.
| Project | Cubic yards | 2 cu. ft. bags | Bags cost | Bulk cost |
|---|---|---|---|---|
| Border bed, 3 × 20 ft, 3 in | 0.56 | 8 | $32 | $23 |
| Tree ring, 6 ft across, 3 in | 0.25 | 4 | $16 | $15 |
| Island bed, 8 ft circle, 3 in | 0.47 | 7 | $28 | $15 |
| Garden bed, 10 × 10 ft, 3 in | 0.93 | 13 | $52 | $30 |
| Front of the house, 4 × 40 ft, 3 in | 1.48 | 20 | $79 | $45 |
| Topping up 200 ft² of beds by 1 in | 0.62 | 9 | $36 | $23 |
| New beds, 500 ft², 3 in | 4.63 | 63 | $250 | $143 |
How much area mulch covers
| Depth | 1 cubic yard | 1.5 cu. ft. bag | 2 cu. ft. bag | 3 cu. ft. bag |
|---|---|---|---|---|
| 1 in | 324 ft² | 18 ft² | 24 ft² | 36 ft² |
| 2 in | 162 ft² | 9 ft² | 12 ft² | 18 ft² |
| 3 in | 108 ft² | 6 ft² | 8 ft² | 12 ft² |
| 4 in | 81 ft² | 4.5 ft² | 6 ft² | 9 ft² |
How deep should mulch be?
The University of Illinois Extension recommends 2 to 4 inches on well-drained ground: 2–3 inches of composted or fine material and 3–4 inches of coarse mulch like wood chips. Iowa State University Extension gives the same 3–4 inches of chips or shredded bark around trees and shrubs on well-drained sites, and 2–3 inches on heavy soils.
- More is not better. Thick layers mat down, keep the soil from drying, and cut the water and oxygen that reach the roots. Illinois lists overmulching among the most common causes of tree decline.
- Keep it off the trunk. Leave at least 4 inches of bare soil around the trunk (6 inches, says Iowa State). Mulch piled against the bark softens it and invites insects, disease and girdling roots.
- Tree rings: spread mulch out to the dripline or as far as you can. Illinois puts a 3-foot radius ring as the maximum for most trees, so a ring 6 feet across.
Topping up old mulch
Mulch breaks down, so beds need more every so often, but not a full new layer. HomeGuide suggests 2–3 inches for beds that already have mulch and 3–4 inches for new ones. Illinois Extension's advice is to measure first: if there is still enough, just rake it to break up matted layers. In the calculator, enter what is already there and it only counts the difference.
Bags or bulk?
A cubic yard is 13.5 bags of 2 cu. ft., so 14 bags: $56 at the regular $3.97, against $30–$40 for a yard in bulk. During the Home Depot sales (4 or 5 bags for $10), the same 14 bags cost $28–$35, and once you add a delivery fee of $50–$150, bags on sale can beat bulk for a few yards.
- Under a cubic yard: bags. They fit in the car and there is no delivery fee.
- Several yards: bulk from a landscape supply yard is usually cheaper and saves a pile of plastic bags. Ask whether delivery is included, or bring a pickup or trailer.
- Dyed or natural: dyed mulch costs about $10 more per yard (This Old House), and cedar can reach $100 a yard.
Frequently asked questions
How many bags of mulch are in a cubic yard?
13.5 bags of 2 cubic feet, the size of the store-brand bags at Home Depot and Lowe's, so you buy 14. With 1.5 cu. ft. bags it is 18, and with 3 cu. ft. bags, 9. A cubic yard is 27 cubic feet: divide 27 by the size printed on the bag.
How much area does a yard of mulch cover?
162 ft² at 2 inches deep, 108 ft² at 3 inches and 81 ft² at 4 inches. A 2 cu. ft. bag covers 8 ft² at 3 inches, which is what the bag label says.
How much mulch do I need for a 10 × 10 area?
At 3 inches deep, 0.93 cubic yards, or 13 bags of 2 cu. ft. At 2 inches, two thirds of that; at 4 inches, a third more.
How deep should mulch be?
2 to 4 inches, according to the University of Illinois Extension: 2–3 inches of fine or composted mulch, or 3–4 inches of coarse wood chips. Iowa State University Extension suggests the thinner end, 2–3 inches, on heavy soils. Deeper layers mat down and keep water and oxygen from the roots.
How much does mulch cost?
Bulk wood mulch runs about $30 a cubic yard undyed and $40 dyed (This Old House); HomeGuide gives a range of $25–$100. A 2 cu. ft. bag is regularly $3.97–$4.48 at Home Depot, and 4 or 5 bags go for $10 during its spring and late-summer sales.
Should mulch touch the tree trunk?
No. Keep at least 4 inches of bare soil around the trunk (Illinois Extension; Iowa State says 6). Mulch piled against the bark, the "mulch volcano", keeps it wet, invites rot and rodents, and can lead to girdling roots. Spread it flat in a ring up to 3 feet out from the trunk.
Sources
- University of Illinois Extension: Proper Mulching Techniques (Tree Care Basics, March 2024)extension.illinois.edu
- Iowa State University Extension: How deep should the mulch layer be around trees and shrubs?yardandgarden.extension.iastate.edu
- HomeGuide: How much does mulch cost? (April 30, 2025)homeguide.com
- This Old House: How much does a yard of mulch cost? (June 8, 2026)thisoldhouse.com
- DealNews: Home Depot mulch sale (August 10, 2026): Vigoro 2 cu. ft. bags regularly $3.97–$4.48dealnews.com