Frequently Asked Questions
Everything you need to know about the Pendulum Calculator.
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.