# How we chose the height while calculating potential energy?

I'm really confused how to chose height when calculating potential energy. If an object is right above a desk, suppose the will we take height from desk?

If we take it from a height $x$ from the desk and the level of desk is $y$ from the ground and we change the position of the object such that now the object is directly above the floor. So will the potential energy change as height changes and if so, we know that potential energy is stored energy.

Will the stored energy increase?

Potential energy stored in a body is relative. We have to first choose the potential at a finite point or infinity. In the case given above, we take potential energy to be 0 at the centre of the Earth. So according to the relation, $PE = mgh$ where $h$ is the height from the centre of the Earth. Generally, we take height from the surface of the Earth and take $9.8 m/s^2$ as the acceleration due to gravity (the $g$ at the surface). Therefore, in your case Potential energy will be $PE = mg(x+y)$.