How to Convert Angles from Degrees to Radians in Excel

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Excel has a number of built-in trigonometric functions that make it easy to find the cosine, sine, and tangent of a right-angle triangle—a triangle containing an angle equal to 90 degrees.

The only problem is that these functions require the angles are measured in radians rather than degrees, and while radians are a legitimate way of measuring angles based on the radius of a circle, they are not something most people work with on a regular basis.

To help the average spreadsheet user get around this problem, Excel has the RADIANS function, which makes it easy to convert degrees to radians.

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RADIANS Function Syntax and Arguments

Screenshot of Excel showing conversion from degrees to radians

A function's syntax refers to the layout of the function and includes the function's name, brackets, and arguments. The syntax for the RADIANS function is:

= RADIANS ( Angle )

The Angle argument is the angle in degrees to be converted to radians; it can be entered as degrees or as a cell reference to the location of this data in your Excel worksheet.

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Excel RADIANS Function Example

Screenshot of Excel showing the Formula Builder

This example uses the RADIANS function to convert a 45-degree angle to radians. The information covers the steps used to enter the RADIANS function into cell B2 of the example worksheet.

=RADIANS(A2)
=RADIANS(45)

Options for entering the function include:

  • Typing the complete function, as shown above, into cell B2.
  • Selecting the function and its arguments using the RADIANS Formula Builder.

Although it is possible to enter the complete function manually, many people find it easier to use the Formula Builder, as it takes care of entering the function's syntax such as brackets and comma separators between arguments.

Using the Formula Builder for RADIANS

  1. Click on cell B2 in the worksheet — this is where the function will be located.
  2. Click on the Formulas tab of the ribbon menu.
  3. Choose Math & Trig from the ribbon to open the function drop-down list.
  4. Click on RADIANS in the list to bring up the Formula Builder.
  5. Click on the Angle line.
  6. Click on Cell A2 in the worksheet to enter the cell reference as the function's argument.
  7. Click Done to complete the function — the answer 0.785398163which is 45-degrees expressed in radians, appears in cell B2.

It is an easy matter to enter the actual data to be used for the argument directly into the dialog box; however, it is usually best not to use actual data for a function's argument because doing so makes it harder to update the worksheet.

An alternative, as shown in row four of the example image, is to multiply the angle by the PI() function and then divide the result by 180 to get the angle in radians.