Radial velocity is the component of the velocity of an object, directed along a line from the observer to the object. Radial velocity formula is defined as (2 x π x n) / 60. It is expressed in radians. Radians per second is termed as angular velocity. Radial velocity equation is based on revolutions per minute (rpm). Usually, it is defined as positive when they are moving away from the radar (outbound) and negative when they are moving towards the radar (inbound).