By Zencalcy Editorial TeamLast reviewed About us
Angular momentum measures how much rotational motion an object has and how hard it is to stop. For a rigid body it is the product of moment of inertia and angular velocity, and in the absence of external torque it stays constant.
Spin momentum from inertia and angular velocity.
L = I ω
L is angular momentum in kg·m²/s, I is moment of inertia and ω is angular velocity in rad/s. For a point mass moving in a circle, L = mvr.
| Symbol | Meaning |
|---|---|
| L | Angular momentum, in kg·m²/s. |
| I | Moment of inertia, in kg·m². |
| ω | Angular velocity, in rad/s. |
The angular momentum is 2 × 10 = 20 kg·m²/s. Halving the inertia by pulling the mass inward doubles the angular velocity if no external torque acts.
Continue with the Angular Velocity Calculator, Circular Motion Period Calculator, or the Angular Momentum Conservation Calculator — or browse more rotational and periodic motion tools and all physics calculators.
Yes, when no net external torque acts. That is why a figure skater spins faster when pulling their arms in: I falls and ω rises to keep L constant.
Results are computed from the standard equations of classical mechanics. Unit conversions use the SI definitions published by NIST. Air resistance is ignored unless the calculator names a drag model.
Reference material used to build and check this calculator:
Last reviewed: September 2026. See how we build and check every tool on the about page.
Free calculator · No signup
Free calculator · No signup
Free calculator · No signup
Free calculator · No signup
Free calculator · No signup
Free calculator · No signup
Content updated: September 2026