It is known from school lessons that mass is a measure of body inertia. If we are pushing two shopping carts of different dimensions, the heavier one will be more difficult to stop. That is, the larger the mass, the more external influences are required, to change the movement of the body. This refers to translational movement when the carriage is moving in a straight line. The mass moment of inertia is analogous to mass and translational motion a measure of the inertia of a body when it rotates around an axis. The moment of inertia depends on the mass, the position of the axis of rotation, and the shape and size of the body.

J = ∫r2dm

The Huygens-Steiner theorem is often used to calculate the mass moment of inertia. It reads: "The moment of inertia of a body around any axis is equal to the sum from the moment of inertia of a body around an axis parallel to any one axis passing through the center of mass and the product of the body mass with the square of the distance between the axes ".

J = JC + md2