How the mulch calculator works
The calculator does the same arithmetic a garden center does when you call for a quote:
- Area of each bed. Length × width for a rectangle. For a circle, 3.1416 × diameter² ÷ 4. For a ring around a tree, the outer circle minus the bare circle at the trunk. If you already know the square footage, pick “I know the square feet”.
- Volume. Total area × depth in feet (inches ÷ 12) gives cubic feet.
- Cubic yards. Cubic feet ÷ 27, because a cubic yard is 3 ft × 3 ft × 3 ft.
- Bags. Cubic feet ÷ the bag size, rounded up. Most bagged mulch is 2 cubic feet; some is 1.5 or 3.
Those steps collapse into one handy formula:
cubic yards = square feet × depth in inches ÷ 324
The 324 comes from 12 inches × 27 cubic feet. Use it to check any result on this site with a phone calculator.
Worked example
You have a 20 × 10 ft bed along the house and want 3 inches of shredded hardwood.
- Area: 20 × 10 = 200 sq ft
- Volume: 200 × 3 ÷ 12 = 50 cu ft
- Cubic yards: 50 ÷ 27 = 1.85 cu yd, so a bulk order of 2 yards
- Bags: 50 ÷ 2 = 25 bags of 2 cu ft (or 17 bags of 3 cu ft)
Now add a second bed: a ring around a maple, 8 ft across with a 1 ft bare circle at the trunk. That ring is about 49.5 sq ft, which adds about 12.4 cu ft, or 0.46 cu yd, at the same depth. Press Add another bed in the calculator, choose “Ring around a tree”, and the totals update.
Mulch needed by bed size
Cubic yards and 2 cu ft bags for common bed sizes, with no extra added. Bags are rounded up.
| Bed area | Yards at 2 in | Yards at 3 in | Yards at 4 in | Bags at 2 in | Bags at 3 in | Bags at 4 in |
|---|---|---|---|---|---|---|
| 50 sq ft | 0.31 | 0.46 | 0.62 | 5 | 7 | 9 |
| 100 sq ft | 0.62 | 0.93 | 1.23 | 9 | 13 | 17 |
| 200 sq ft | 1.23 | 1.85 | 2.47 | 17 | 25 | 34 |
| 300 sq ft | 1.85 | 2.78 | 3.70 | 25 | 38 | 50 |
| 500 sq ft | 3.09 | 4.63 | 6.17 | 42 | 63 | 84 |
| 1,000 sq ft | 6.17 | 9.26 | 12.35 | 84 | 125 | 167 |
How much one cubic yard of mulch covers
| Depth | Square feet per cubic yard | Square feet per 2 cu ft bag |
|---|---|---|
| 1 inch | 324 | 24 |
| 2 inches | 162 | 12 |
| 3 inches | 108 | 8 |
| 4 inches | 81 | 6 |
| 6 inches | 54 | 4 |
The mulch coverage calculator works the other way round: tell it how much mulch you have and it gives the area.
Picking a depth
Most beds look finished and keep weeds down at 2 to 3 inches. Fine-textured mulch such as pine bark fines packs tighter, so 2 inches is often plenty. Coarse material such as large pine bark nuggets and wood chips lets more light through and breaks down slowly, so 3 to 4 inches is common. If you are topping up a bed that already has mulch, measure what is left with a ruler and only add the difference. The mulch depth guide has the details, including how to mulch around trees without piling it against the trunk.
Bulk or bags?
The cost section of the calculator compares the two. Enter your local bulk price per yard, the delivery fee and the price of the bag you would buy. The bulk figure uses your yardage rounded up to the next half yard, because that is how most landscape yards sell it. There is more on what drives the price on the mulch cost calculator page.
Mulch types in the calculator
The type you choose doesn’t change the volume: a yard of cedar and a yard of pine bark are both 27 cubic feet. It sets the depth the calculator suggests and, for pine straw, switches the result to bales. Rubber mulch has its own bag size and much shallower depth in beds; see the rubber mulch calculator. For a quick tour of what each mulch is good for, see types of mulch.
These are estimates. Bag sizes are printed on the bag, and bulk loads can settle in the truck, so a "yard" of loose, fluffy mulch may look a little short once it's spread. If your supplier gives you their own coverage figure, use theirs.
Questions people ask
- How do I calculate how much mulch I need?
- Multiply the bed's length by its width to get square feet, multiply by the depth in inches, then divide by 324. The answer is cubic yards. A 20 by 10 foot bed at 3 inches is 200 × 3 ÷ 324 = 1.85 cubic yards.
- How many square feet does a yard of mulch cover?
- One cubic yard covers about 162 square feet at 2 inches deep, 108 square feet at 3 inches and 81 square feet at 4 inches.
- How many bags of mulch are in a yard?
- A cubic yard is 27 cubic feet, so it equals 13.5 bags of 2 cubic feet, 9 bags of 3 cubic feet or 18 bags of 1.5 cubic feet.
- How deep should mulch be?
- Two to three inches suits most shrub and flower beds. Coarse material such as large pine bark nuggets or wood chips can go 3 to 4 inches. Keep mulch a few inches away from tree trunks and plant stems.
- Should I order extra mulch?
- Fresh mulch settles a little after rain, and beds are rarely perfectly even. Rounding up to the next half yard or the next whole bag is usually enough; add 5 to 10 percent if the beds are sloped or the edges are hard to measure.
- Is it cheaper to buy mulch in bulk or in bags?
- It depends on your local prices and the delivery fee. Enter a price per yard, a delivery fee and a price per bag in the calculator and it shows which is cheaper for your beds. Small jobs often favor bags; larger ones usually favor bulk.