# Same birthday probability (chart) Calculator

## Calculates a table of the probability that one or more pairs in a group have the same birthday and draws the chart.

 n ~ persons in a group
 (1) the probability that all birthdays of n persons are different.$\normal \\\vspace{5}\hspace{20}\overline{p}(n)={\large\frac{364}{365}}\times{\large\frac{363}{365}}\times{\large\frac{362}{365}}\times\cdots\\\hspace{50}={\large\frac{365\times364\times363\times\cdots\times(365-n+1)}{365^n}}\\\hspace{50}={\large\frac{365!}{365^n(365-n)!}}\\$(2) the probability that one or more pairs have the same birthday.$\normal\\\vspace{5}\hspace{20}p(n)=1-\overline{p}(n)\\$This calculation ignores the existence of leap years.

Sending completion

To improve this 'Same birthday probability (chart) Calculator', please fill in questionnaire.
Male or Female ?
Male Female
Age
Under 20 years old 20 years old level 30 years old level
40 years old level 50 years old level 60 years old level or over
Occupation
Elementary school/ Junior high-school student
High-school/ University/ Grad student A homemaker An office worker / A public employee
Self-employed people An engineer A teacher / A researcher
A retired people Others
Useful?
Very Useful A little Not at All
Purpose of use?