How to Calculate Landscape Blocks Needed Using the Radius

Your landscaping needs might require some basic knowledge of geometry. For instance, if you need to make a circular wall out of landscaping blocks, you might wonder how many blocks you will need for the project. Start by measuring the radius of the circle you want to create and deciding what size of landscaping blocks you will use. From there, calculating the number of blocks needed to create one layer of the circle is easy.

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Landscaping well requires the frequent use of geometry.

Step 1

Decide what size landscaping blocks you will be using. They come in many sizes, from 5 inches to 24 inches long. This, along with the radius of circle you are trying to create, will be the largest determining factor for how many blocks you will need.

Step 2

Determine the radius of the circle of blocks. Stand in the center of the circular area and fasten the end of your tape measure to an object on the ground. Extend the tape measure to the farthest point that you will need enclosed by the circle of landscaping blocks. Read the measurement on the tape measure; this is the radius of the circle.

Step 3

Plug the value for your radius into the equation for the perimeter of the circle: 2 x pi x radius. For example, if your radius is 20 feet, then you would use this equation: 2 x 3.14 x 20 feet = 125.6 feet.

Step 4

Divide the length of your perimeter by the length of the type of landscaping block you will be using. For example, if you are using 10-inch blocks, which are 10/12 or 0.83 foot, then you would calculate 125.7 / 0.83 = 151.4 blocks. Then round up your number to the nearest whole number, 152.