Physics

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Pendulum Kinetic Energy Calculator.

Calculate ideal simple-pendulum kinetic energy gained between a release angle and a current angle.

On-device calculationNo signup
01

Set your values

Results update as you type.

Height drop: 0.118782 m

Height drop

0.000000m
Kinetic energy: 1.164857 J

Kinetic energy

0.000000J

Results update automatically as you type.

Use Cases

Physics homework and lab verification

Quickly compute the kinetic energy of a pendulum at a specific point in its swing, useful for checking experimental results or solving textbook problems.

Example: A 0.5 kg bob on a 1.2 m string released from 30° has how much kinetic energy at 10°?

Designing pendulum-based mechanisms

Estimate the energy available at a certain angle for clock mechanisms, toys, or educational demonstrations, helping to choose appropriate mass and length.

Example: Determine if a 2 kg bob on a 0.8 m pendulum provides enough energy at 5° to drive a small gear.

Frequently Asked Questions

How does the pendulum kinetic energy calculator work?
It uses the principle of conservation of mechanical energy. You input the bob mass, pendulum length, release angle, and current angle. The calculator finds the vertical height difference between these angles and computes the kinetic energy gained as mass × gravity × height difference.
What units should I use for the inputs?
Use kilograms for bob mass, meters for pendulum length, and degrees for both release and current angles. The calculator outputs kinetic energy in joules (J).
Can I use this calculator for a real pendulum with friction?
No, this calculator assumes an ideal simple pendulum with no air resistance or friction at the pivot. Real pendulums lose energy, so the actual kinetic energy will be slightly less than the calculated value.

Tips & Common Mistakes

Tips

  • Ensure the current angle is less than or equal to the release angle; otherwise, the pendulum would be higher than its release point, which is physically impossible for a simple pendulum.
  • Use consistent units: kilograms for mass, meters for length, and degrees for angles. The calculator converts degrees to radians internally.
  • For small angles (less than about 15°), the motion is nearly simple harmonic, but this calculator works for any angle up to 90°.
  • Remember that the kinetic energy is zero at the release angle (if released from rest) and maximum at the lowest point (current angle = 0°).

Common Mistakes to Avoid

  • Entering the current angle larger than the release angle, which would imply the pendulum gained potential energy without external work.
  • Using grams for mass instead of kilograms, leading to results that are off by a factor of 1000.
  • Forgetting that the length must be in meters; using centimeters will produce incorrect energy values.

Last updated: August 13, 2026