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Gardening Guide: How to Determine How Much Mulch You Need

Mulch | Landscape Improvements

The use of mulch is proven to be beneficial in gardening. It helps maintain moisture and coolness in the soil, keeps weeds from growing, and adds appeal to your garden bed. There are also organic mulches that help enhance the soil’s drainage, structure, and nutrient-holding capacity as they decompose.

However, it’s important to know how to determine the amount of mulch you’ll need to be effective. The use of excessive mulch can cause several issues.

Importance of Using The Right Amount of Mulch

There is no doubt that mulch is very effective in gardening. But, using too much can lead to problems. Here is a list of what can happen if you use an excessive amount of mulch:

  • It can decrease the amount of soil oxygen for roots and suffocate them, eventually causing them to wither.
  • Roots deprived of oxygen and water can grow into mulch as they seek the nutrients they need to live. When this happens, the mulch will dry out during the summer, and the roots that grew into the mulch will die.
  • Mulch that is clumped against the tree’s trunk and shrubs will keep the bark moist underneath. The moisture can cause decay and open a possible means of access for diseases and insects.
  • Light watering will not work as it will only wet the mulch layer, leaving the soil dry.
  • Excessive mulch can prevent the breaking of dormancy during spring by keeping a cooler temperature around the roots.
  • Can provide a place for voles to hide.


If you don’t want to encounter any of these issues, you’ll need to know how to determine how much mulch you need.

Let’s discuss that.

How to Calculate the Right Amount of Mulch to Use

To avoid the use of excessive mulch, you can follow this simple step-by-step guide. You will only need a measuring tape or wheel and a calculator for this process.

Step 1: Decide on the type of mulch to use

There are different types of mulch that you can use for gardening and landscaping, such as shredded bark chips, compost, pine straw, wood chips, newspaper, grass clippings, and many more. It is best to match the mulch that you will use with which plants you are planning to grow on your garden bed. Once you decide on the type of mulch you will be using; you can follow a mulch calculator formula to determine the right amount you should put on your garden bed.

Step 2: Measure the square footage of your garden area

The square footage of your garden area where you will put the mulch is essential in calculating the appropriate amount to use. Calculating the total square footage will depend on the shape of your garden bed.

If you have a square or rectangular garden, simply multiply the length by its width. Make sure to use a foot as your metric. On the other hand, if you have a circular garden bed, measure the distance from the center to the edge and take that as your radius. After that, multiply it by itself and to the value of pi (π) or 3.14.

Step 3: Decide how thick the mulch layer should be

The next step is to determine how deep the mulch layer should be. If it’s going around trees and shrub beds, it’s highly suggested to have three to four inches of mulch layer. Meanwhile, the recommended thickness is one to three inches for vegetable and flower beds.

Step 4: Know if you will use a bagged or bulk mulch 

The formula you will use to determine how much mulch you need will depend on whether you are using a bagged mulch or a bulk mulch. Bagged mulches in the US are sold in cubic feet, while bulk mulches are measured in cubic yards.

Bulk Mulch Calculator Formula

You can use this formula and step-by-step calculation process to determine how much mulch you need when you buy mulch in bulk.

  1. Multiply the square footage of your garden bed by the measure of the thickness of the mulch layer that you want to add to it.
  2. Divide the answer to step one by 324


Doing these two steps will give you the bulk mulch you need in cubic yards. So, for example, you have a rectangular garden bed. Its length measures 40 feet, while its width measures 20 feet. The square footage that you should get is 800 feet.

After that, say you want to plant flowers on that garden bed. The appropriate mulch layer thickness is from one to three inches, and you want it to be at two inches. To get the total amount of mulch you need, you will multiply 800 by 2 and divide it by 324. The answer that you should get is 4.84 cubic yards- this is the amount of bulk mulch that you need.

Bagged Mulch Calculator Formula

If you are buying a bagged mulch instead, this is how to determine how much mulch you need:

Multiply the square footage of your garden bed to one of these numbers, based on how thick you want your mulch layer to be:

1 inch deep = 0.083

2 inches deep = 0.167

3 inches deep = 0.25

4 inches deep = 0.33

5 inches deep = 0.417


That should give you the right amount of mulch you need. So, for example, you have a circular garden bed with a 10 feet radius. Multiply that by itself and to 3.14 to get the square footage. You should have 314 by doing that.

Once you have the square footage, determine the thickness of mulch you want to apply. Suppose you want a 4-inch deep mulch layer, then you should multiply 314 by 0.33. That will give you 103.62 cubic feet of bagged mulch.

Call Landscape Improvements to Add The Right Amount of Mulch to Your Garden

Landscape Improvements is the best that you can go to for landscaping requirements in Florida. Worry no more about the numbers and calculating the right amount of mulch that you need to put in your garden. We can do that for you with our Mulch Redressing services.

Call us at 407-606-7326 to learn more about our services. Or you can email us directly at information@landscapeimprove.com.

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