Mulch calculator.
Beds, tree rings and play sets, topped up rather than piled on.
A mulch order is rarely one bare bed: a border still holding last year's inch, rings around trees whose trunks must stay clear, perhaps the ground under a swing set. This calculator subtracts what is already down, takes play-area depths from the CPSC's home playground handbook, and prices bags against a delivered yard.
0302 / Volume
- Volume to add
- 97.7 cu ft
- Ordered, with extra
- 97.7 cu ft · 3.62 cu yd
- Bags
- 49 bags of 2 cu ft
- Bulk order
- 3.62 cu yd
- Bags or bulk
- No prices entered
- Trips
- No bed volume entered
- Wheelbarrow
- 17 loads of 6 cu ft
Volumes are what to add once the layer already down is subtracted; play areas are filled deep enough to settle to the handbook minimum.
0203 / Areas
ONE SCALE PER CELLMulch by area
| Area | Size | Area each | Copies | Depth asked | Already there | Added | Volume |
|---|---|---|---|---|---|---|---|
| Beds | 40′ 0″ × 3′ 0″ | 120.0 sq ft | 2 | 3″ | 1″ | 2″ | 40.0 cu ft · 1.48 cu yd |
| Tree rings | Radius 3′ 0″, trunk 10″, gap 3″ | 26.9 sq ft | 3 | 3″ | 0″ | 3″ | 20.2 cu ft · 0.75 cu yd |
| Known area | Area typed in | 150.0 sq ft | 1 | 3″ | 0″ | 3″ | 37.5 cu ft · 1.39 cu yd |
Bags against bulk
| Option | Quantity | Volume bought | Cost |
|---|---|---|---|
| Bags | 49 × 2 cu ft | 98.0 cu ft | — |
| Bulk | 3.62 cu yd | 97.7 cu ft | — |
| Cheaper | No prices entered | Break-even | No prices entered |
NIST's method-of-sale regulation fixes volume as the unit of mulch. The break-even line gives the volume at which a delivered yard, fee included, costs less than bags.
Tree ring check
Each ring is checked against the trunk gaps the publishers print and against NCUFC's minimum ring radius for a small, medium and large tree.
| Source | Minimum | Your ring |
|---|---|---|
| University of Maryland Extension | Gap 3″ | Meets it |
| UC Marin Master Gardeners (UC ANR) | Gap 6″ | Short by 3″ |
| NCUFC | Gap 1″ | Meets it |
| Casey Trees | Gap 3″ | Meets it |
| City of Maple Grove, Minnesota | Gap 3″ | Meets it |
| NCUFC, small tree | Radius 3′ 0″ | Meets it |
| NCUFC, medium tree | Radius 8′ 0″ | Short by 5′ 0″ |
| NCUFC, large tree | Radius 12′ 0″ | Short by 9′ 0″ |
Depths by publisher
Depth and fine-mulch ceiling as each publisher prints them, a dash where none is given. Trunk gaps and ring radii are compared in the ring check above.
| Publisher | Depth | Fine mulch |
|---|---|---|
| Penn State Extension | 2–4″ | 1–2″ |
| University of Maryland Extension | 1–3″ | — |
| Iowa State University Extension | 2–4″ | — |
| UC Marin Master Gardeners (UC ANR) | — | up to 2″ |
| NCUFC | 2–4″ | — |
| Casey Trees | 3″ | — |
| City of Maple Grove, Minnesota | 3″ | — |
Playground surfacing (CPSC)
Depth follows the equipment height, and the first fill is deeper because loose mulch packs down.
| Equipment | Maintained depth | Initial fill | Surfaced extent |
|---|---|---|---|
| Under 4′ 0″ | 6″ | 8″ | 6′ 0″ beyond the equipment, all sides |
| 4′ 0″ to 8′ 0″ | 9″ | 12″ | 6′ 0″ beyond the equipment, all sides |
| To-fro swing | By height | By height | 2 × top bar height, front and back |
Bag sizes and coverage
| Bag | 1″ deep | 2″ deep | 3″ deep | 4″ deep | Bags per cubic yard | Bags for this order |
|---|---|---|---|---|---|---|
| 1.5 cu ft | 18.0 sq ft | 9.0 sq ft | 6.0 sq ft | 4.5 sq ft | 18.0 | 66 |
| 2 cu ft · your bag | 24.0 sq ft | 12.0 sq ft | 8.0 sq ft | 6.0 sq ft | 13.5 | 49 |
Two borders, three rings and a bed: 3.62 cubic yards
The two borders are 40 by 3 feet, 240 square feet. With an inch still down and a 3-inch target, 2 inches go on: 40 cubic feet, where a full layer would have asked 60 and left 4 inches, Penn State's ceiling. Three rings reaching 3 feet around 10-inch trunks, with a 3-inch bare gap, add 20.2 cubic feet; the typed bed adds 37.5. The order is 97.7 cubic feet, 3.62 cubic yards: 49 bags of 2 cubic feet or 66 of 1.5. New beds start with the soil calculator.
Under a play set the depth is not a choice
An 8 by 10 foot set 7 feet high needs 9 inches of wood mulch kept, so a 12-inch first fill, over the set plus 6 feet on every side: 440 square feet, 440 cubic feet, 16.3 cubic yards. A swing hung from an 8-foot bar needs twice that height in front and behind.
Questions asked while planning a mulch order
What is the 3-3-3 rule for mulch?
Around a tree: mulch about 3 inches deep, out to a radius of about 3 feet, with a 3-inch bare gap around the trunk. Casey Trees and the City of Maple Grove, Minnesota, both publish it with those figures. The gap is where other publishers differ: NCUFC asks for 1 to 2 inches, UC Marin for 6 to 12, and NCUFC's minimum ring radius is 3 feet only for small trees.
How can I calculate how much mulch I need?
Square feet times the depth in inches, divided by 12, gives cubic feet; divide by 27 for cubic yards, or divide square feet times inches by 324 directly. A 100 square foot bed at 3 inches is 25 cubic feet, 0.93 cubic yard. Subtract the depth already on the ground first, and measure rings as rings.
How much do 20 bags of mulch cover?
Twenty 2-cubic-foot bags hold 40 cubic feet: 160 square feet at 3 inches, 240 at 2 inches. Twenty 1.5-cubic-foot bags hold 30 cubic feet: 120 square feet at 3 inches, 180 at 2. The coverage table on this page does the same for the bag size you enter.
How much will 25 bags of mulch cover?
At 3 inches, 25 bags of 2 cubic feet cover 200 square feet and 25 bags of 1.5 cubic feet cover 150. At 2 inches the same bags cover half as much again, and at 1.5 inches twice as much.
How many bags of mulch is 4 yards?
Four cubic yards are 108 cubic feet: 54 bags of 2 cubic feet or 72 bags of 1.5. At that volume a delivered load is worth pricing; the bags-or-bulk table shows where it becomes cheaper at your prices.
How many 2 cu ft bags of mulch are in a cubic yard?
13.5, since a cubic yard is 27 cubic feet, so 14 whole bags. Bags of 1.5 cubic feet take 18. A bag labeled in liters converts at 28.32 liters to the cubic foot: a 50-liter bag holds 1.77 cubic feet.
Can it measure a round bed or a tree ring?
Yes, and for the ring around a tree, which is a circle with a hole. A full circle 3 feet in radius is 28.3 square feet; leave a 3-inch gap around a 10-inch trunk and it is 26.9. The ring row takes the outer radius, the trunk and the gap; set the trunk and the gap to 0 and it becomes a plain round bed.
What about a triangular bed?
Work out its area, base times height divided by 2, and type it in the area row: a corner bed 12 feet along one side and 8 feet along the other is 48 square feet. The row then takes the depths like any other bed.
How do I read the size on a mulch bag?
By volume: NIST's method-of-sale regulation has mulch sold by the cubic foot or cubic yard, or by the liter or cubic meter. The product line read for this page comes in 1.5 and 2 cubic feet. Enter the size off the label in cubic feet or liters and the bag count follows.
Should I remove old mulch before putting new mulch down?
Measure it first. Penn State says some old mulch may need removing before a new layer and that new over old each year is the same as one layer too deep; Scotts suggests removing old mulch past 4 inches; NCUFC says not to add any if the layer is already sufficient, and to rake the matted top instead. Enter the depth still there and the page adds only the difference.
What month is the best time to mulch?
Penn State Extension and UC Marin Master Gardeners both name the middle of spring, once the soil has warmed, as the best time for trees, while noting mulch can go down at almost any time of year. The calculator does not depend on the season; the depth left over from last year does.
How many inches of mulch for a playground?
For a home play set, the CPSC asks for at least 9 inches of wood mulch or chips under equipment up to 8 feet high, and at least 6 inches under equipment lower than 4 feet. A 12-inch first fill packs down to about 9, so that is what to order for; the play rows do it from the equipment height.
Does it calculate rubber mulch?
No. The CPSC’s public handbook gives shredded rubber its own depth, 6 inches for a 10-foot fall, and notes that it does not pack down the way wood does, so the 12-inch first fill used for wood does not carry over to it. The page covers wood mulch and chips only.
What the order does not cover
- Flat ground and one depth per area; slopes and berms are not modeled.
- Rings are circles around one trunk; beds under several trees are typed as an area.
- Publishers' depths and gaps are quoted, not ranked; none of them is a standard.
- Play rows follow the CPSC home handbook for wood mulch or chips under equipment up to 8 feet; taller equipment, rubber mulch, sand, pea gravel and mats are not modeled, and overlapping zones between a set and a swing are not merged.
- No weight is computed, so trips are counted by volume; no prices, fees or minimum orders are preset.
- How much a mulch decomposes in a year is not predicted: the existing depth is measured by you.