How this calculator works
The particle model uses a velocity perpendicular to the radius, so the angular momentum magnitude is mass times speed times radius. The rigid-body model uses moment of inertia about the specified axis. This scalar tool finds magnitudes; the direction follows the right-hand rule. An oblique particle velocity needs its tangential component.
Formula
L = m v_t r for a particle; L = I omega for fixed-axis rigid-body rotation.
Worked example
A 3 kg particle moving tangentially at 4 m/s, 2 m from the origin, has 24 kg m²/s of angular momentum. A rotor with I = 5 kg m² at 3 rad/s has 15 kg m²/s.
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Frequently asked questions
Which origin should I use?
Choose the point or axis about which you want angular momentum. Changing it can change the answer.
Is angular momentum energy?
No. Angular momentum has units kg m²/s; rotational energy has units joules.
What if velocity points towards the centre?
Its tangential component is zero, so angular momentum about that centre is zero.