Case 1
- Bed area (square feet)
- 100sq ft
- Depth (inches)
- 3in
13bags
Open with these valuesMulch Calculator
13bags of 2 ft³
Result: 13 bags of 2 ft³Area in square feet times depth in feet gives cubic feet; divide by the 2 cubic feet a standard bag holds and round up. 100 sq ft at 3 inches is 25 cubic feet, so 13 bags. Two to three inches is the usual depth for a bed — deeper smothers shallow roots.
The numbers at a glance
Held fixed: Bed area (square feet) 100.0 sq ft.
| Depth (inches) (in) | Result (bags) |
|---|---|
| 0.0 | 0 |
| 1.0 | 5 |
| 2.0 | 9 |
| 3.0Your value | 13 |
| 4.0 | 17 |
| 5.0 | 21 |
| 6.0 | 25 |
Worked examples
Case 2
- Bed area (square feet)
- 200sq ft
- Depth (inches)
- 2in
17bags
Open with these valuesCase 3
- Bed area (square feet)
- 50sq ft
- Depth (inches)
- 3in
7bags
Open with these valuesHow it's calculated
bags = ⌈(area × depth ÷ 12) ÷ 2 ft³ per bag⌉
- StepEnter the bed area in square feet — length × width for a rectangle.
- StepSet the depth in inches; 2 to 3 inches suits most beds.
- StepArea × depth ÷ 12 is the volume in cubic feet.
- ResultDivide by the 2 cubic feet a bag holds and round up to whole bags.
What this number means
Square feet and inches, not metres
Bagged mulch is sold by the cubic foot, so this calculator takes the area in square feet and the depth in inches. One square metre is about 10.76 square feet and one centimetre about 0.39 inches.
Depth moves the number as much as area
A cubic yard covers 324 square feet at one inch, 162 at two inches and 108 at three. Halve the depth and you cover twice the area.
Bulk and bags are measured differently
Bulk mulch is sold by the cubic yard, bags by the cubic foot. A cubic yard is 27 cubic feet, so it equals 13.5 standard bags — which is why bulk is usually cheaper for a large bed.
Commonly misread
The deeper the mulch, the better it works.
Fine wood and bark mulches should not go more than 2 to 3 inches deep, or they smother the roots. Coarse material such as pine bark nuggets lets air through and can go to 4 inches.
Every bag holds 2 cubic feet.
This calculator assumes that, but bags of 1.5 and 3 cubic feet are sold too. Check the label and work from the cubic feet in the middle column of the table instead.
I entered my bed in square metres.
The area field is square feet, and the two are not interchangeable. Convert first — one square metre is about 10.76 square feet.
Reference table
| Area, depth | Volume | Bags |
|---|---|---|
| 20, 3 | 5 ft³ | 3 |
| 50, 3 | 12.5 ft³ | 7 |
| 100, 2 | 16.67 ft³ | 9 |
| 100, 3 | 25 ft³ | 13 |
| 200, 2 | 33.33 ft³ | 17 |
Questions
How much mulch do I need?
Multiply the area in square feet by the depth in feet, which is the depth in inches divided by 12. 100 sq ft at a 3-inch depth is 25 cubic feet, about 0.93 cubic yards, or 13 standard bags.
Why does this calculator work in feet and inches?
Because bagged mulch is sold that way and the bag states its size in cubic feet. Enter the area in square feet, not square metres — one square metre is about 10.76 square feet, and one centimetre about 0.39 inches.
How deep should mulch be?
Fine wood and bark mulches should not go more than 2 to 3 inches deep — enough to suppress weeds and hold moisture without smothering roots. Coarse material such as pine bark nuggets lets air through and can go to 4 inches.
How many bags are in a cubic yard?
A cubic yard is 27 cubic feet, and a standard bag holds 2, so a cubic yard is 13.5 bags. That is why bulk mulch is usually cheaper than bags for a large bed.
How much area does a cubic yard cover?
A cubic yard covers 324 square feet at one inch, so 108 square feet at 3 inches and 162 at 2 inches. Coverage and depth trade off directly — halve the depth and you cover twice the area.
Are all bags 2 cubic feet?
No, and this calculator assumes they are. Bags of 1.5 and 3 cubic feet are also sold, so check the label and work from the cubic feet in the middle column of the table if yours differs.
Sources and last check
Information, not professional advice.