๐ฏ Fun & Games
Birthday Probability Calculator
The birthday problem surprises people because we picture our own birthday rather than every possible pair. With twenty-three people there are two hundred and fifty-three pairs, and it takes only that many chances for a match to become more likely than not.
How it works
People in the group
Days in the year
People who need the same birthday
Probability of a shared birthday
Probability nobody shares
Pairs in the group
Odds against a match
People needed for 50 per cent
Frequently asked questions
How do I use the Birthday Probability Calculator?
Fill in the fields above โ the result recalculates instantly as you type. Everything runs in your browser, so the values you enter are never collected or stored.
Is this calculator free?
Yes. It is completely free, requires no account, and works on phones, tablets and desktops.