About the Mulch Calculator
This mulch calculator works out how much mulch you need to cover a garden bed, tree ring or landscape border at the depth you choose. Enter the length and width of a rectangular bed (or the diameter of a round one) and the depth in inches, and it returns the volume in cubic feet and cubic yards along with the number of bags to buy.
It is useful for homeowners planning a spring refresh, landscapers quoting a job and anyone deciding whether bulk delivery or bagged mulch from the garden center is cheaper. Bulk mulch is usually sold by the cubic yard, while bags are labeled in cubic feet (most commonly 2 cu ft), so the tool shows both and compares the cost.
Most shredded bark and wood-chip mulches perform best at 2–4 inches deep: enough to suppress weeds and hold moisture without smothering roots. Keep mulch a few inches away from tree trunks and plant stems. For several separate beds, calculate each one and add the results together.
With the default inputs, the mulch needed is 1.85 cu yd. Change any value above to recalculate instantly.
How to use the mulch calculator
- 1Choose a rectangular bed or a round tree ring.
- 2Measure the length and width (or diameter) in feet.
- 3Pick a depth — 3 inches is a good default for most beds.
- 4Select the bag size sold at your store and enter local prices.
- 5Compare the bulk and bagged cost and order a little extra for uneven ground.
Formula and method
The area is length × width for a rectangular bed, or π × (diameter ÷ 2)² for a round bed or tree ring. Multiplying the area by the depth (converted from inches to feet by dividing by 12) gives the volume in cubic feet. A cubic yard is 3 ft × 3 ft × 3 ft = 27 cubic feet, so dividing by 27 converts to the unit bulk suppliers use.
Bags are rounded up to whole bags because you cannot buy part of one. Bulk cost is the exact cubic-yard volume times your price; many suppliers sell in half- or whole-yard increments and add delivery, so round up when ordering.
- Area
- Bed area in square feet
- Depth
- Mulch depth in inches
- 27
- Cubic feet in one cubic yard
Worked examples
20 × 10 ft bed at 3 inches
A 200 sq ft bed at 3 inches deep needs 200 × 3 ÷ 12 = 50 cubic feet, which is 50 ÷ 27 ≈ 1.85 cubic yards. That is 25 bags of 2 cu ft ($100 at $4 a bag) or about $74 of bulk mulch at $40 per yard.
8 ft tree ring at 4 inches
A circle 8 ft across has an area of π × 4² ≈ 50.3 sq ft. At 4 inches deep that is about 16.8 cubic feet (0.62 cubic yards), so you need 9 bags of 2 cu ft.
40 × 5 ft border at 2 inches with 3 cu ft bags
A 200 sq ft border topped up with 2 inches needs 33.3 cubic feet, or about 1.23 cubic yards. With 3 cu ft bags that rounds up to 12 bags.
Frequently asked questions
How many bags of mulch are in a cubic yard?+
A cubic yard is 27 cubic feet, so it equals 13.5 bags of 2 cu ft mulch, 9 bags of 3 cu ft mulch or 18 bags of 1.5 cu ft mulch.
How deep should mulch be?+
For most beds 2–3 inches of fine mulch or 3–4 inches of coarse bark or wood chips is enough to suppress weeds and retain moisture. Deeper layers can suffocate roots and encourage rot.
How much area does a cubic yard of mulch cover?+
One cubic yard covers about 324 sq ft at 1 inch deep, 162 sq ft at 2 inches, 108 sq ft at 3 inches and 81 sq ft at 4 inches.
Is bulk mulch cheaper than bags?+
For jobs above roughly 2–3 cubic yards, bulk mulch is usually cheaper per yard even after a delivery fee. For small top-ups, bags avoid the fee and are easier to handle.
Should I remove old mulch before adding new?+
Usually not. If the old layer has broken down, simply top it up to reach a total depth of 2–4 inches. Remove it only if it is matted, moldy or already too deep.