Calculators
Calculators

Birthday Paradox Simulator

Why 23 people give a 50% chance of a shared birthday.

Private by design

Your inputs stay on your device and are not sent to our servers. Optional usage analytics does not receive your files or tool inputs.

Preparing tool

How to use Birthday Paradox Simulator

  1. Set the group size, or try a class of 30.
  2. Press Run to simulate random groups.
  3. Compare the simulated share with theory and see each group on a calendar.
Read the detailed guide →

What are the limits of Birthday Paradox Simulator?

Runs entirely in your browser with random numbers from your device; results vary from run to run, as they should.

YOUR BROWSER, YOUR CHOICE