Where do we use radian as a unit? This topic contains 1 reply, has 2 voices, and was last updated by Surjeet Sankararaj 5 years ago. Author Posts July 30, 2013 at 8:29 am #2997 sankarParticipant Points: 105 Can anyone please explain where do we use radian as a unit? August 7, 2013 at 7:50 pm #3009 Surjeet SankararajKeymaster Points: 631 Radian is the standard SI unit of plane angle. It is used in several mathematical and engineering problems. One radian is equal to 180/π degrees. Author Posts You must be logged in to reply to this topic.