Pendulum Calculator
Work out the swing period of a pendulum from its length.
The rhythm of a swing
A pendulum's period — the time for one full swing — depends almost entirely on its length, not its weight or how far it swings. This works out the period from the length, the physics behind grandfather clocks, metronomes and the classic playground swing.
Enter the pendulum's length to see its period.
The surprising independence from weight
The counterintuitive and beautiful fact, which Galileo is said to have noticed watching a swinging lamp, is that a pendulum's period does not depend on how heavy it is or, for small swings, how wide the swing is — only on its length and gravity. A longer pendulum swings more slowly. This is exactly why pendulum clocks keep good time: the regular period is set by the fixed length, and adjusting a clock means adjusting that length.
Pendulum Calculator FAQ
Does a heavier pendulum swing faster?
No — remarkably, the period depends only on length and gravity, not on weight or, for small swings, how far it swings.
Why do pendulum clocks keep good time?
Because the fixed length sets a regular period. Adjusting the clock means adjusting the pendulum's length.
Is anything uploaded?
No. The calculation happens in your browser.