1. The problem statement, all variables and given/known data I hope I can explain this properly: 1. Let's say you're given the mass moment of inertia of some non-uniform 3-dimensional object. 2. The moment is relative to coordinate system "CS1", with origin at the object's center of mass and about axes x, y and z. 3. Say there is a second coordinate system, "CS2", with a different origin from CS1, but with all axes parallel to those of CS1. What I'm really interested in is the object's moment of inertia relative to CS2, which I understand can be calculated using the Parallel Axis Theorem. However: 4. Now, say the object is rotated about its own center of mass (origin of CS1) by some angle, θ, about some arbitrary axis, X. The object will now have a new mass moment of inertia relative to the coordinate system CS2. THE QUESTION: is there a way to use the initial mass moment of inertia of the object and the angle and axis of rotation to calculate the new moment of inertia of the object relative to CS2? 2. Relevant equations This is more of a concept question, so no equations. 3. The attempt at a solution My idea is to treat the initial moment of inertia of the object as a 3D vector and apply the same rotation to the vector as was applied to the object. Then I would use the rotated value of the vector as the new moment of inertia of the object and use the Parallel Axis Theorem to calculate the moment in coordinate system CS2. Would this give the correct result? Thanks in advance for any help.