How to Solve for Radius in Excel

By Aurelio Locsin

Use Excel to automate solving circle formulas.
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If you’re involved in such business as interior design, technical illustration, furniture making, or engineering, you may occasionally need to calculate the radius of a circle or sphere given other dimensions of the object. Although you may typically calculate using pen and paper, or calculator, you can also use Excel to solve for the missing variable.

Click on a cell and enter the constant of the radius formula. For example, click on cell B2 and enter the diameter of your circle.

Enter one of the following formulas to solve for radius, without the quotation marks, in an adjacent cell. For example, if you entered your constant in B2, enter the formula in B3. For <cell>, substitute the location of the constant. This example would use “B2” for <cell>.

Enter “=<cell>/2” if <cell> contains the diameter of the circle.

Enter “=<cell>/2*PI()” if <cell> contains the circumference of the circle.

Enter “=SQRT(<cell>/PI())” if <cell> contains the area of the circle in square units. For example, <cell> can equal square feet, which produces the result in feet.

Enter “=POWER(<cell>*0.75/PI(),1/3)” where <cell> contains the volume of the sphere in cubic units. For example, <cell> can equal cubic inches, which produces the result in inches.

Press “Enter” to view the result of your equation in the formula cell.