Guess My Birthday · a Mind Reading trick
I'm going to find your birthday.
Keep it secret. Don't tell me the month or the day. Just do a little arithmetic — a calculator or your phone is fine.
Using a calculator? Press = after each instruction before moving to the next step.
Read-aloud isn't available in this browser. Everything stays on screen.
About this experience
Guess My Birthday asks you to do a few quick calculations with your birth month and day, then type the single number you end up with. From that number alone, your birthday appears.
The numbers you add change between rounds — there are 400 different versions — but every real month and day works, including February 29. No year is needed, and nothing you type leaves your device.
Not just birthdays
After the reveal you can try any other date that matters — an anniversary, a friend's birthday, a favourite day. Every month and day works the same way, and you never have to say what the date means.
Perform it for a friend
Performer Mode gives you a private script and a quick way to read the answer, so you can find a friend's birthday from one number.