In PostgreSQL, the radians() function converts from degrees to radians.

The radian is the SI (International System of Units) unit for measuring angles. One radian is just under 57.3 degrees, and a full circle has just over 6.28 radians (2π).

Syntax

The syntax goes like this:

radians(dp)

Where dp is a double precision value that represents the degrees you want converted to radians.

Example

Here’s an example of how it works.

SELECT radians(45);

Result:

0.7853981633974483

Here, we see that 45 degrees is equal to 0.7853981633974483 radians.

Negative Values

You can also pass negative values.

SELECT radians(-45);

Result:

-0.7853981633974483

Expressions

Here’s an example that uses an expression.

SELECT radians(80 + 10);

Result:

1.5707963267948966

Large Values

You can pass values that are larger than a full circle.

SELECT radians(3000);

Result:

52.35987755982988

Full Circle

In this example I provide the number of degrees in a full circle.

SELECT radians(360);

Result:

6.283185307179586

Pass Another Function

The previous example can also be done using the degrees() function, which converts from degrees to radians.

SELECT radians(degrees(6.283185307179586));

Result:

6.283185307179586

Pi

As mentioned, a radian is 2π. Therefore, passing a value of 180 (degrees) to the function returns pi. We can verify this by using the pi() function to return the pi constant.

SELECT 
  pi(),
  radians(180);

Result:

 pi               | radians
------------------+------------------
3.141592653589793 | 3.141592653589793

Similarly, we can pass 360 and that will be 2π.

SELECT 
  pi() * 2,
  radians(360);

Result:

 pi               | radians
------------------+------------------
6.283185307179586 | 6.283185307179586