Simple pendulum period calculator
Enter the pendulum length from the pivot to the center of the bob. The result does not depend on the mass.
Loading the tool…
Processing and privacy: The result is calculated inside your browser and your data is not sent to any server.
How to use it
- Enter pendulum length and gravitational acceleration g.
- The result appears straight away and updates as you edit.
- Copy the result, or copy a link that keeps the same values to share it.
How it is calculated
T = 2π × √(L ÷ g), frequency f = 1 ÷ T, where L is the length and g the gravitational acceleration.
Example
Inputs: Pendulum length = 1 m, Gravitational acceleration g = 9.80665 m/s². Result: Period: 2.0064 s; Frequency: 0.4984 Hz; Swings per minute: 29.9042.
Limits and caveats
- Accurate for small swings (below about 15 degrees); larger swings take slightly longer.
- Assumes a light, non-stretching string and ignores air resistance.
Questions about this tool
Does the bob mass change the period?
No. For a simple pendulum the period depends only on length and gravity.
What length gives a 2 second period?
About 0.994 m with standard gravity. It is called a seconds pendulum because each one-way swing takes a second.
How can I measure g with a pendulum?
Measure the length and the time for 20 swings, divide to get T, then g = 4π² L ÷ T².