⏱️Pendulum Calculator
Find the period, frequency, or length of a simple pendulum using T = 2π√(L/g).
Runs entirely in your browser. No data is sent to a server.
Free Pendulum Calculator
Curious how long it takes a pendulum to swing back and forth? Our free pendulum calculator finds the period, frequency, or length of a simple pendulum instantly using T = 2π√(L/g). Enter the length and gravity, or work backwards from a known period, and see the result immediately.
Presets for Earth, Moon, and Mars gravity let you quickly compare how a pendulum would behave on different worlds, and a live animated pendulum shows the swing visually as you adjust the values. The calculator also flags when your swing angle is too large for the standard small-angle formula to stay accurate.
Whether you're studying simple harmonic motion or just experimenting with the physics of a swing, this tool gives clear, accurate answers with the working shown. No sign-up, no downloads, no limits. See the About page or the FAQ for more.
About the Pendulum Calculator
Features
Solve for T, L, or g
Any two values give the third.
Gravity presets
Earth, Moon, Mars, or a custom value.
Animated pendulum
Swings at a rate scaled from the computed period.
Small-angle check
Warns when the swing amplitude exceeds ~15°.
Frequently Asked Questions
How does the pendulum calculator work?
Enter any two of period, length, or gravitational acceleration, and it solves for the third using T = 2π√(L/g).
Is it free?
Completely free, no sign-up, downloads, or limits.
What is the pendulum period formula?
T = 2π√(L/g), where L is the pendulum length and g is gravitational acceleration.
Does it work for other planets?
Yes, presets for Earth, Moon, and Mars gravity are included, plus a custom gravity field.
Does mass affect the period?
No — for a simple pendulum, the period depends only on length and gravity, not the mass of the bob.
What is the small-angle approximation?
The formula assumes swings under about 15°; the calculator flags when your input suggests this assumption may not hold.
Does it show the steps?
Yes, the formula and substitution with your actual values are shown for every calculation.
What if I enter a negative length?
Length and gravity must be positive; invalid values are flagged.
Is my data stored?
No; everything runs in your browser and isn't stored or sent anywhere.
Does it work on mobile?
Yes, fully responsive, with the pendulum animation scaling to fit the screen.