Mulch Calculator: How Much Mulch Do You Need?
Enter your garden beds and depth to get cubic yards or bags of mulch, and see whether bags or bulk delivery costs less for your yard.
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Mulch is sold two ways: in 2 or 3 cubic foot bags at the garden center, or loose by the cubic yard from a landscape supplier. Either way, you are buying volume, so the question is how much space your beds take up at the depth you want. The calculator handles rectangular beds, round tree rings and triangular corners, and it compares the cost of bags with bulk.
The formula
For each bed:
cubic feet = area in square feet × depth in inches ÷ 12
Then divide by 27 to get cubic yards, because a cubic yard is 3 × 3 × 3 = 27 cubic feet.
The UC Marin Master Gardeners give the same formula and these handy reference points for one cubic yard:
| Depth | One cubic yard covers |
|---|---|
| 1 inch | about 325 sq ft |
| 2 inches | about 160 sq ft |
| 3 inches | about 100 sq ft |
| 4 inches | about 80 sq ft |
How deep should mulch be?
It depends on the mulch. The UC Marin Master Gardeners recommend:
- Fine mulch (pieces under half an inch, like shredded bark fines): no more than 2 inches, so air and water still reach the roots.
- Coarse mulch (wood chips, nuggets): about 4 to 6 inches if you mainly want to smother weeds in open areas. Around shrubs and perennials, 3 inches is a common compromise.
- Grass clippings or shredded leaves: 2 inches at most, because they mat down.
- Poorly drained soil: use less.
If you are topping up old mulch, measure what is still there and only add the difference. Piling fresh mulch on every year is how beds end up 8 inches deep.
A worked example: front beds and a tree ring
Two shapes: a 20 x 4 ft bed along the front of the house and an 8 ft circle around a tree. Shredded bark at 3 inches.
- Bed: 20 × 4 = 80 sq ft
- Tree ring: π × 4² = 50.3 sq ft (the calculator asks for the diameter, 8 ft)
- Total area: 130.3 sq ft
- Volume: 130.3 × 3 ÷ 12 = 32.6 cu ft, or 1.21 cubic yards
- In 2 cu ft bags: 32.6 ÷ 2 = 16.3, so 17 bags
At $4.50 a bag, that is $76.50. Bulk at $45 a yard would be about $54, but a delivery fee wipes out that saving on a job this small. At these prices bulk saves about $15.75 a yard, so delivery starts to pay for itself somewhere between 4.5 and 9 cubic yards, depending on the fee.
Bags or bulk?
LawnStarter's 2026 price data:
- Bulk mulch: $30 to $135 per cubic yard, often 15% to 30% less per yard when you buy more.
- Bagged mulch: $3.25 to $6.50 per 2 cu ft bag. It takes about 13.5 bags to make a cubic yard, which works out to roughly 35% more than bulk.
- Delivery: usually a flat $70 to $140.
- Professionally installed: about $77 to $94 per cubic yard, including delivery and basic labor.
Bags are easier to carry and store, and you can buy exactly what you need. Bulk is cheaper and comes in one load, but you need a place for the pile and a wheelbarrow.
Where not to put mulch
- Against tree trunks. Keep mulch 6 to 12 inches away from the base of trees and shrubs so the root flare stays visible. A "mulch volcano" piled against the trunk can harm the tree.
- Right against the house. The UC Marin Master Gardeners advise keeping organic mulch at least 5 feet from the house and using non-flammable material like gravel or pavers in that zone. Our gravel calculator handles that strip.
- Over thick weeds. Pull or smother them first. Mulch slows new weeds but does not kill established ones.
Measuring odd-shaped beds
- Curved beds: split them into a rectangle plus a circle or half-circle. For a half-circle, enter a full circle and halve that part of the result.
- Long, narrow strips: measure length and average width.
- Kidney shapes: measure the longest length and the average width. It will be close enough for mulch.
Frequently asked questions
How many bags of mulch are in a yard?
About 13.5 bags of 2 cubic feet, or 9 bags of 3 cubic feet.
How much area does a bag of mulch cover?
A 2 cu ft bag covers 12 sq ft at 2 inches, 8 sq ft at 3 inches or 6 sq ft at 4 inches.
How much mulch for a 10 x 10 bed?
At 3 inches: 100 sq ft × 3 ÷ 12 = 25 cu ft, which is 0.93 cubic yards or 13 bags of 2 cu ft.
Should I remove old mulch first?
Not usually. Rake it to loosen it and top it up to the depth you want. Remove it if it is matted, moldy or already deeper than about 4 inches.
Next step
Planning a path or a strip of stone near the house? The gravel calculator works the same way but in tons. For a patio, see the paver calculator.
Prices are US figures from 2026 and vary by region and supplier.
