How to use this calculator
- Choose whether you measure in feet and inches or meters and centimeters.
- Pick how many beds you’re covering, up to three.
- For each bed, choose its shape: a rectangle (length and width), a circle (diameter) or a triangle (base and height), and enter the measurements.
- Enter the depth of mulch you want. Three inches is the default.
- Optionally adjust the bag price and bulk price per cubic yard, plus any delivery fee, to compare the two ways of buying.
The result shows the volume in cubic yards, the number of 2 and 3 cubic foot bags, and how the same beds work out at 2, 3 and 4 inches deep. That last table answers the question you’re likely to have in the store aisle: what if I go a little thinner?
The formula
Mulch is sold by volume, so the calculation is area times depth. Because depth is measured in inches and area in square feet, you divide by 12 to get cubic feet, then by 27 to get cubic yards. Together that’s a single divisor of 324.
The area depends on the shape of the bed:
- Rectangle: length × width.
- Circle: π × (diameter ÷ 2)².
- Triangle: base × height ÷ 2, where the height is measured at a right angle to the base.
For bags, divide the cubic feet by the bag size and round up to a whole bag.
Worked example
The calculator starts with two beds: a 20 × 4 foot strip along the front of the house and a ring 8 feet across around a tree, both 3 inches deep.
- Strip: 20 × 4 = 80 sq ft.
- Tree ring: π × 4² = 50.27 sq ft.
- Total area: 80 + 50.27 = 130.27 sq ft.
- Volume: 130.27 × 3 ÷ 12 = 32.57 cubic feet.
- Cubic yards: 32.57 ÷ 27 = 1.21 cubic yards.
- Bags: 32.57 ÷ 2 = 16.3, so 17 bags of 2 cubic feet, or 32.57 ÷ 3 = 10.9, so 11 bags of 3 cubic feet.
At the example prices of $4.50 a bag and $45 a cubic yard, the 17 bags cost $76.50 and the same amount in bulk costs $54.28 before any delivery fee. Your prices will differ, so replace the examples with what your store or landscape yard charges.
How much mulch for common bed sizes
Bag counts are rounded up to whole bags.
| Bed area | 2 in deep | 3 in deep | 4 in deep |
|---|---|---|---|
| 50 sq ft | 0.31 yd³ · 5 bags | 0.46 yd³ · 7 bags | 0.62 yd³ · 9 bags |
| 100 sq ft | 0.62 yd³ · 9 bags | 0.93 yd³ · 13 bags | 1.23 yd³ · 17 bags |
| 200 sq ft | 1.23 yd³ · 17 bags | 1.85 yd³ · 25 bags | 2.47 yd³ · 34 bags |
| 300 sq ft | 1.85 yd³ · 25 bags | 2.78 yd³ · 38 bags | 3.70 yd³ · 50 bags |
| 500 sq ft | 3.09 yd³ · 42 bags | 4.63 yd³ · 63 bags | 6.17 yd³ · 84 bags |
| 1,000 sq ft | 6.17 yd³ · 84 bags | 9.26 yd³ · 125 bags | 12.35 yd³ · 167 bags |
Bag counts in this table are for 2 cubic foot bags. For 3 cubic foot bags, a 100 square foot bed needs 6, 9 or 12 bags at 2, 3 or 4 inches.
Coverage per bag and per yard
| Depth | One 2 cu ft bag | One 3 cu ft bag | One cubic yard |
|---|---|---|---|
| 2 in | 12 sq ft | 18 sq ft | 162 sq ft |
| 3 in | 8 sq ft | 12 sq ft | 108 sq ft |
| 4 in | 6 sq ft | 9 sq ft | 81 sq ft |
Choosing a depth
Extension horticulturists at the University of Illinois and the University of Vermont recommend a layer of 2 to 4 inches. Within that range:
- 2 inches is enough to refresh a bed that still has some mulch from last year.
- 3 inches suits most new beds, holding in moisture and blocking weed seeds from light.
- 4 inches works for coarse bark nuggets or wood chips, which settle and break down more slowly.
More isn’t better. A layer much deeper than 4 inches can mat down and keep water and air from reaching the roots. Keep mulch a few inches back from tree trunks and the stems of shrubs; the cone-shaped “mulch volcano” piled against a trunk traps moisture against the bark and invites rot and pests.
Bags or bulk?
Bags are sold by volume, and the size is printed on the front. The 2 cubic foot bag is the standard size at home centers, and some mulches come in 3 cubic foot bags or smaller 1.5 cubic foot bags. If yours is a different size, divide the cubic feet in the result by the number on the bag.
Bulk mulch is sold by the cubic yard at landscape supply yards and garden centers. It’s often cheaper per yard than bags once you need more than a yard or two, but compare the total with delivery, and check whether the supplier has a minimum order. For a small bed, or if you can’t spread the mulch the same day, bags are easier to handle and store. If you’re also laying a path or a stone border, the gravel calculator works the same way for stone and sand.
Tips for measuring
- Measure in feet and convert inches. 12 feet 6 inches is 12.5 feet.
- Split odd shapes. A kidney-shaped bed is roughly a rectangle with a half circle at each end. Two half circles make one full circle with the same diameter.
- Subtract nothing for plants. Shrubs take up little of the volume, and a little extra mulch is handy for top-ups.
- Check your total area with the square footage calculator if you have many beds; then enter the total as one rectangle (for example 250 × 1 ft).
Assumptions and limitations
- Beds are treated as flat, with an even depth. Sloped beds use a little more.
- Bag volumes are the loose volume printed on the bag. Fresh, fluffy mulch settles a little after watering, which is one more reason to round up.
- Costs are editable examples, not quotes. Prices vary by region, material and season.
- For any other material sold by the cubic yard, such as topsoil or fill, the cubic yard calculator handles boxes, holes and wedges.
Sources
- University of Illinois Extension: Proper mulching techniques
- University of Vermont Extension: Beware the mulch volcano
- Scotts Nature Scapes Color Enhanced Mulch, 2 cu ft bag (product listing)
Frequently asked questions
How many bags of mulch are in a cubic yard?
A cubic yard is 27 cubic feet, so it takes 13.5 bags of 2 cubic feet or 9 bags of 3 cubic feet to make one yard. In practice you'd buy 14 of the 2 cubic foot bags, because stores don't sell half bags.
How much area does a bag of mulch cover?
A 2 cubic foot bag covers 12 square feet at 2 inches deep, 8 square feet at 3 inches, or 6 square feet at 4 inches. A 3 cubic foot bag covers half as much again, 18, 12 or 9 square feet at those depths.
How deep should mulch be?
University extension services recommend 2 to 4 inches. Fine materials like compost do well at the shallow end and coarse bark or wood chips at the deeper end. Keep mulch a few inches away from tree trunks and plant stems, and don't pile it up in a cone around trees.
How much mulch do I need for 100 square feet?
At 3 inches deep, 100 square feet takes 25 cubic feet of mulch, which is 0.93 cubic yards, 13 bags of 2 cubic feet or 9 bags of 3 cubic feet. At 2 inches it's 9 bags of 2 cubic feet, and at 4 inches it's 17.
Is bulk mulch cheaper than bags?
Usually, once a job gets past a cubic yard or so, but it depends on your local prices and the delivery fee. Enter both prices in the calculator to compare. Bags are easier to carry for a small bed and keep well if you don't spread them right away.
How do I measure a round or odd-shaped bed?
For a circle, such as a ring around a tree, measure straight across the widest point and choose Circle. Split curved or L-shaped beds into rectangles, circles and triangles, enter each one as a separate bed, and the calculator adds them up.
Updated November 2026. Results are estimates for educational purposes and depend on the inputs you provide.