Rotational Kinetic Energy Calculator

Enter moment of inertia and angular speed or RPM to calculate rotational energy, angular momentum, and the equivalent rotational speed.

Moment of inertia I (kg·m²)

Angular speed

Angular-speed unit

—KEᵣ = ½Iω²

—Angular momentum

—RPM

—rad/s

—Moment of inertia

This ideal rigid-body calculation assumes the supplied moment of inertia is about the actual rotation axis.

Physics model preflight

Check the governing model before trusting the number

ideal rigid-body rotation

KEᵣ = ½Iω² · L = Iω

Reading the current native inputs…

Moment of inertia must be positive for this UI model; supplied I must match the actual axis. This is an idealized educational model: unit consistency and valid inputs do not guarantee that omitted effects are negligible in a real system.

State the model before trusting the number

Classical formulas are only as good as their assumptions and units. Air resistance, damping, deformation, non-constant forces and measurement uncertainty are not silently invented when the selected model does not include them.

Governing physics model

KEᵣ = ½Iω² · L = Iω — ideal rigid-body rotation.

How to verify the result

Check L = Iω and KE = ½Iω². Doubling angular speed doubles angular momentum but quadruples rotational energy.

Domain and assumption boundary

Moment of inertia must be positive for this UI model; supplied I must match the actual axis. The calculator does not silently add drag, damping, deformation, varying fields, relativistic effects, measurement uncertainty, or geometry that the selected model does not contain.