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Mulch Calculator: How Many Bags or Cubic Yards Do You Need?
Pick your bed shape, punch in the size and depth, and get the exact cubic yards you need — plus a bags-vs-bulk comparison using standard 2 cu ft bags, always rounded up. The math runs entirely in your browser: no sign-up, no tracking.
By HowMuchBuild Editorial TeamCalculation reviewedUpdated October 2026
feet
feet
inches — 2–3″ is typical for maintained beds
10% is a safe default — mulch settles and beds are rarely perfectly even.
Estimated cost
What will it cost?
Enter your local store prices — prices vary by region.
Bulk mulch
1.22 cu yd
—
Bagged mulch
17 bags
—
Estimate — prices vary by store and region. Check your local store for current pricing.
You need
1.22cu yd
Exact volume: 1.11 cu yd · 120 sq ft at 3″ deep
or 17 bags (2 cu ft bags · 13.5 bags per cu yd · exact pour needs 15)
| Buy option | Exact | With 10% waste |
|---|---|---|
| Bulk (cubic yards) | 1.11 cu yd | 1.22 cu yd |
| 2 cu ft bags | 15 bags | 17 bags |
Rule of thumb: bags suit small beds; bulk usually wins past about 2 cubic yards.
How we calculated it
- Area = 10 ft × 12 ft = 120 sq ft
- Volume = 120 sq ft × 0.25 ft (3″ deep) = 30 cu ft
- Cubic yards = 30 ÷ 27 = 1.11 cu yd
- With 10% waste: 30 × 1.10 = 33 cu ft = 1.22 cu yd
- Bags (2 cu ft each): 33 ÷ 2 = 16.5 → round up = 17 bags
Estimates for planning. Bag sizes vary — check the cu ft printed on your bag (most are 2 cu ft). Bulk yards can run light if the pile has settled, so the waste allowance covers that too.
Worked example: 10×12 ft bed at 3 inches deep
A typical flower bed against the house. Here is the full arithmetic, step by step:
- Area: 10 ft × 12 ft = 120 sq ft
- Depth in feet: 3 ÷ 12 = 0.25 ft
- Volume: 120 × 0.25 = 30 cu ft
- Cubic yards: 30 ÷ 27 = 1.11 cu yd
- Bags (2 cu ft): 30 ÷ 2 = 15 bags
- With 10% waste: 30 × 1.10 = 33 cu ft → 33 ÷ 27 = 1.22 cu yd, or 33 ÷ 2 = 16.5 → 17 bags
Mulch coverage chart: one cubic yard
One cubic yard is exactly 27 cubic feet. Deeper beds eat yards fast:
| Depth | 1 cu yd covers | Notes |
|---|---|---|
| 2″ | 162 sq ft | light top-off |
| 3″ | 108 sq ft | rule of thumb: ≈ 100 sq ft |
| 4″ | 81 sq ft | fresh bed depth |
| 6″ | 54 sq ft | rarely recommended |
The exact math at 3 inches is 27 ÷ 0.25 = 108 sq ft. The industry rounds to 100 sq ft per yard at 3″ as a rule of thumb — deliberately a touch conservative, which beats coming up half a yard short.
Common bed sizes at 3″ deep
Bags below use standard 2 cu ft bags; figures exclude waste:
| Bed | Area | Cubic yards | 2 cu ft bags |
|---|---|---|---|
| 5×10 ft rectangle | 50 sq ft | 0.46 | 7 |
| 10×12 ft rectangle | 120 sq ft | 1.11 | 15 |
| 10×20 ft rectangle | 200 sq ft | 1.85 | 25 |
| 20×20 ft rectangle | 400 sq ft | 3.70 | 50 |
| 10 ft diameter circle | 78.5 sq ft | 0.73 | 10 |
| 8×10 ft triangle | 40 sq ft | 0.37 | 5 |
Bags vs. bulk: which should you buy?
Since 27 ÷ 2 = 13.5, every cubic yard of bulk equals about fourteen 2 cu ft bags. Bags are grab-and-go with no delivery minimum, which suits small beds and apartments. Bulk is delivered by the cubic yard and generally costs less per yard — the savings usually win from about 2 cubic yards upward. A word of caution: a bulk pile settles and can run a little light, so keep the waste allowance on when ordering bulk.
The formulas
Rectangle bed
Area = Length × Width (feet). Volume = area × (depth ÷ 12).
Circle bed
Area = π × (diameter ÷ 2)². Measure straight across the widest point.
Triangle bed
Area = ½ × base × height — height is the perpendicular height, not the slanted edge.
Cubic yards and bags
Cubic yards = volume (cu ft) ÷ 27. Bags = ⌈ volume ÷ 2 ⌉ for standard 2 cu ft bags — always round up.
Frequently asked questions
How many bags of mulch are in a cubic yard?
13.5, by the math: a cubic yard is 27 cubic feet and a standard mulch bag is 2 cubic feet (27 ÷ 2 = 13.5). In practice you'd buy 14 bags, since you can't buy half a bag.
How much area does one cubic yard of mulch cover?
Exactly 108 square feet at 3 inches deep (27 ÷ 0.25). The industry rule of thumb rounds this to about 100 square feet per yard at 3″ deep — slightly conservative, which is what you want when ordering.
How deep should mulch be?
2–3 inches is the standard recommendation for maintained beds; fresh beds being mulched for the first time often go 3–4 inches. More than 4 inches can smother roots and stay soggy.
Should I buy mulch in bags or in bulk?
Bags win for small beds — they're easy to move and there's no minimum. Bulk (delivered by the cubic yard) usually costs less per yard once you need around 2 cubic yards or more. At 13.5 bags per yard, the crossover point shows up fast.
How many bags of mulch do I need for a 10×10 area?
At 3 inches deep: 10 × 10 = 100 sq ft, × 0.25 ft = 25 cubic feet. That's 25 ÷ 2 = 12.5 → 13 bags (or 0.93 cubic yards in bulk).
Do all mulch bags hold 2 cubic feet?
No — check the bag. 2 cu ft is the most common size, but 1.5 and 3 cu ft bags exist. Divide your total cubic feet by the number printed on your bag and round up.
Will mulch settle after I spread it?
Yes. Fresh mulch settles and decomposes noticeably in the first weeks — which is exactly why the calculator includes a waste and settling allowance. Top off beds each season rather than over-buying up front.
How deep should you spread it?
General guidance: 2–3 inches for beds you top off every year, 3–4 inches when mulching bare soil for the first time. Spread it evenly, and keep it pulled back a few inches from trunks and stems — piled-up "mulch volcanoes" trap moisture against bark. Because mulch settles and decomposes, measure to your target depth after spreading, not to the depth of the fresh pile in the truck.
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