When to use this calculator
Find kinetic energy stored in rigid-body rotation. Requires moment of inertia about the actual rotation axis.
Explore the force, energy & machines calculators for other questions in this topic. For a related calculation, use the Rotational Power Calculator: Find shaft mechanical power from torque and angular velocity.
PUTTING IT INTO PRACTICE
Rotational Kinetic Energy: a worked example
The values below are an illustrative example, not a recommendation. Replace them with measurements or assumptions that match your question.
| Input | Example value |
|---|---|
| Moment of inertia (kg·m²) | 2 |
| Angular speed (rad/s) | 5 |
| Result | 25 J |
- Check the input labels and enter the example values above.
- Apply the relationship: Energy = moment of inertia × angular speed²/2.
- The result is 25 J, rounded for display.
How to interpret your result
Requires moment of inertia about the actual rotation axis.
Distinguish net force from individual forces and specify the direction of displacement. Work can be negative. Force multiplication does not create extra energy because motion distance and losses also matter.
Frequently asked questions
Is mechanical advantage the same as efficiency?
No. Mechanical advantage compares forces; efficiency compares useful output energy or power with the corresponding input.
When is the rotational kinetic energy calculator useful?
Find kinetic energy stored in rigid-body rotation. Requires moment of inertia about the actual rotation axis.
How do I use the rotational kinetic energy calculator?
Enter moment of inertia (kg·m²), angular speed (rad/s). The result updates automatically. Use the units shown beside each input; the example values illustrate the method.
Which formula does this calculator use?
Energy = moment of inertia × angular speed²/2.
What should I check before using the result?
Requires moment of inertia about the actual rotation axis.
How are results rounded?
Scalar numbers display up to six decimal places, with scientific notation for very large or small values. Text, fraction, date and schedule outputs use the format described on the tool. Intermediate calculations use JavaScript floating-point arithmetic. Keep sensible precision for your measurements.
Further reading
For background on this topic, see OpenStax: work and energy ↗. This is a topic reference, not an external review or endorsement of this tool.
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