# Calculation during conservation of angular momentum

I have seen that when a person is rotating while sitting on a spinning chair, his angular momentum is conserved. What I'm not getting is through what point I am to calculate the angular momentum: is it any point on the axis or any point of choice?

I tried it this way that when a body is in uniform circular motion, its angular momentum is conserved only at the center and not any other point as the perpendicular distance between point and $v$ will change,but I'm not able to find the point when a person is spinning or when a collision is taking place.

• About any point whatsoever. Take your rotating person on a chair. To make it truly a closed system, put the person and chair in outer space. The angular momentum in any inertial reference frame, about any point (call it $A$) in that reference frame, is the sum of the angular momentum of the person/chair about their center of mass, and the angular momentum due to the motion of the person/chair center of mass relative to $A.$ This sum never changes. – Ben51 Jan 28 '18 at 16:14