Mulch Calculator
Enter your bed dimensions. Results update as you type.
2 to 4 in is typical for garden beds. Keep mulch a few inches back from trunks and stems.
Estimate only. Organic mulch breaks down over time and needs topping up about once a year.
A cubic yard of mulch covers 162 square feet at 2 inches deep, or 108 square feet at 3 inches. The one-inch difference changes your order by a third. Get the depth wrong and you either run short mid-bed or haul home bags you don’t need.
The calculator above turns your bed measurements into cubic yards, cubic feet, liters, and bag counts in one step. This guide covers the formula behind those numbers, how depth changes by project, what mulch costs in bulk versus bags, and the mistakes wasting both.
On This Page
- How the Calculator Works
- Depth Guide by Project
- Bulk vs. Bagged: What Mulch Costs
- Organic vs. Inorganic Mulch
- Avoid These Mulch Mistakes
- Frequently Asked Questions
How the Calculator Works
For a rectangular bed, multiply length by width to get the area, then multiply by depth in inches. Divide by 324 to get cubic yards in one step, since 324 comes from 27 cubic feet per yard times 12 inches per foot.
Example: a 10-by-10-foot bed at 3 inches deep covers 100 square feet. Multiply by 3, divide by 324, and the order comes to about 0.93 cubic yards.
For a circular bed, find the radius (half the diameter), then use the formula area = pi x radius squared. Run this area through the same depth math.
Two coverage numbers are worth memorizing: one cubic yard spread at 1 inch covers 324 square feet, and the same yard spread at 4 inches covers about 81 square feet. Use those to sanity-check whatever the calculator gives you before you order.
Depth Guide by Project
Depth depends on the job, not the size of the bed. A fresh bed with bare soil needs more material up front than a bed you’re topping off.
| Project | Recommended depth |
|---|---|
| Established beds (annual refresh) | 2 to 3 in |
| New or bare-soil beds | 3 to 4 in |
| Walkways and play areas | 4 to 5 in |
| Around tree trunks | 2 to 4 in, doughnut shape |
Horticulturists set the 2 to 4 inch range for a reason: oxygen exchange. Pile mulch deeper than 4 inches and roots near the surface start to suffocate, especially around new plantings. Walkways are the one exception, since foot traffic compacts a thicker layer down within weeks.
Tree mulch deserves its own rule. Spread the layer flat in a ring, and leave a gap of 2 to 3 inches between the mulch and the trunk. Piling mulch up against the bark in a cone, often called mulch volcano, traps moisture against the trunk and invites rot and pests underneath.
Bulk vs. Bagged: What Mulch Costs
Bulk mulch runs 25 to 100 dollars per cubic yard for material alone, with most homeowners paying 30 to 80 dollars depending on type. Delivery adds 50 to 150 dollars per load, and most suppliers set a minimum order of 3 to 5 cubic yards.
A standard bag holds 2 cubic feet and costs 2 to 8 dollars. Filling a full cubic yard takes 13.5 bags, which lands the bagged total around 40 to 90 dollars, often 20 to 40 percent more than the bulk price for the same volume.
| Mulch type | Bulk price per cubic yard |
|---|---|
| Standard hardwood | 30 to 45 dollars |
| Cedar | 40 to 55 dollars |
| Dyed mulch | 35 to 50 dollars |
| Rubber | 80 to 120 dollars |
The break-even point lands around 2 to 3 cubic yards, roughly 300 square feet at a 3-inch depth. Order less than this amount, and bags often beat bulk once you count the delivery fee. Order more, and bulk wins almost every time.
Organic vs. Inorganic Mulch
Organic mulch covers bark and wood chips. The material feeds soil while breaking down, a good fit for flower beds and vegetable gardens, though this same breakdown means a yearly top-up to hold depth.
Inorganic mulch covers rubber and stone. Neither one breaks down or feeds the soil, but both last for years with little upkeep, which makes them a fit for pathways and play areas rather than planting beds.
Pick organic where plants are growing and the soil benefits from the breakdown. Pick inorganic where the priority is durability and low maintenance.
Avoid These Mulch Mistakes
Most overorders and shortfalls come down to a short list of habits.
- Building a mulch volcano around tree trunks instead of a flat ring with a gap at the base.
- Adding a full new layer without measuring how much old mulch is still there.
- Mixing units mid-calculation, like length in feet and depth in inches without converting first.
- Filling a large bed with bags instead of pricing out bulk delivery first.
Each one shows up the same way: a yard looking fine in May and a trunk rotting by August.
Get the Number Right Before You Order
Volume comes from one formula: area times depth, divided by 324 when depth is in inches. Depth depends on the project, from 2 inches for an established bed to 4 inches for bare soil, never more. Bulk delivery beats bags once an order passes about 2 to 3 cubic yards, and a flat ring beats a volcano around every tree on the property. Enter your measurements into the calculator above to get an exact number before you place an order.
Frequently Asked Questions
How many bags of mulch are in a cubic yard?
A standard bag holds 2 cubic feet, so a full cubic yard takes 13.5 bags. Larger 3-cubic-foot bags need 9 bags per yard.
How deep should mulch be?
Established beds need 2 to 3 inches. New or bare beds need 3 to 4 inches. Keep total depth under 4 inches anywhere, since deeper layers risk suffocating roots.
Is bulk mulch cheaper than bagged mulch?
Yes, for any bed over roughly 300 square feet at 3 inches deep, or about 2 to 3 cubic yards. Smaller orders often save money in bags once delivery fees are factored in.
How often should I replace mulch?
Organic mulch decomposes within a year, so top up the layer annually. Plan a full replacement every 3 to 5 years, or sooner if you see mold, fungus, or pests in the old layer.
What is mulch volcano and why is it a problem?
Mulch volcano is the practice of piling mulch up against a tree trunk in a cone shape. The trapped moisture invites rot and pests, and the buildup risks suffocating roots near the surface. Spread mulch in a flat ring instead, with a gap of a few inches around the trunk.
