Knowing how much mulch, compost, or amendment to purchase for your garden is always a bit of a guess, but you can make it an educated one by using these two measurements:

- The square footage of your garden
- The desired depth, in inches, of mulch or amendment

### Measure the Area of Your Garden

**Squares and Rectangles:**Multiply width by length**Triangles:**Measure the two sides that meet at a right angle. Multiply the length of one side by 1/2 the length of the other side. It doesn’t matter which is which.

**Circles:**Measure the circle’s radius (½ way across the center of the circle). Multiply the radius by itself. Then multiply that number by 3.14, to get the circle's area. A circle's area equals pi (3.14) multiplied by the radius squared.**Curves and irregular shapes:**Weave a rope, hose or extension cord along the borders and then straighten them out to create a more regular shape. Use one of the formulas above. You may need to break the garden into smaller sections and add them together.

### Adding Amendments to New Gardens

If you are starting a new garden, you will want to add amendments to the entire area of the garden. Use the actual square footage for your calculations below.

### Mulching or Amending an Existing Garden

Once you know the total square footage of your garden, approximate the percentage of the garden that is not occupied by plants. (Ex. 1/8, 1/4...) Multiply the actual square footage by the percentage not occupied by plants.

The resulting square footage is the number you will use for your calculations below.

**Example:**

- Actual square footage = 800 sq. ft.
- Area not occupied by plants = 1/4
- 800 x 1/4 (.25) = 200 sq. ft.

### Estimating Mulch Sold by the Cubic Yard

- Decide how deep you want your mulch (2", 3"...).
- Use the chart below and select the number of inches of coverage.

- Look across to the corresponding number under "Materials Sold by Cubic Yard".
- Divide the square footage of your garden by the number from the chart.

**Example:**

- Your garden has an area of 200 sq. ft. and you want 4 inches of mulch.
- The corresponding number on the chart for 4 inches of mulch is 80.
- Divide your sq. footage (200 sq. ft.) by 80.
- 200 divided by 80 = 2.5.

You would need 2 ½ cubic yards of mulch to cover a 200 sq. ft. garden with 4 inches of mulch.

### Estimating Mulch Sold Mulch by the Bag

Bagged mulch is sold by either weight or cubic volume.

- There are 27 cu. ft. in a cubic yard.
- The average 40 lb. bag of mulch is approximately equal to 1 cu. ft.

So whether you are buying 1-cubic-foot bags or 40-pound bags, the math is the same: multiply the number of cubic yards you need by 27.

**Example:**

In our example above, we needed 2.5 cubic yards.

Multiply the number of cubic yards you need (2.5) by 27.

2.5 x 27 = 67.5 bags of cubic foot or 40-pound bags of mulch.

**Note:** If you are purchasing mulch in 2-cubic-foot bags, you would multiply by 13.5. (2.5 x 13.5 = 33.75).

**Conversion Numbers**

Coverage Depth | Sq. Ft. / Cu. Yard |

1" | 324 |

2" | 162 |

3" | 108 |

4" | 81 |

5" | 65 |

6" | 54 |

7" | 46 |

8" | 40 |