🎂 Age Calculator
Enter a birth date to get an exact age, total days lived, and a countdown to the next birthday.
How the years, months and days are counted
The calculator subtracts calendar parts rather than dividing a day count, which is how people actually say their age. It takes the year, month and day of the "as of" date and subtracts the birth date's, borrowing when a part comes out negative: a negative day count borrows the length of the month before the "as of" date, a negative month count borrows twelve from the year.
Born 1 January 1990, measured on 8 September 2026, that gives 36 years, 8 months and 7 days - plus 13,399 total days, 1,914 whole weeks, and a Monday as the day of birth.
Dates, timezones and leap days
- Both dates are read at local midnight, so the answer never shifts by a day because of your timezone or a daylight saving change.
- The total-days figure is rounded, so a clock change inside the span cannot push it half a day out.
- Leave "as of" empty and it uses today. Set it to a past or future date to get someone's age on that day.
Frequently asked questions
How old am I if I was born in 1990?
You turn 36 during 2026. If your birthday has not happened yet this year you are still 35 - the calculator settles it by comparing the month and day, not just the year.
How many days old am I?
Roughly your age in years times 365.25. Someone born on 1 January 1990 has lived 13,399 days by 8 September 2026.
What day of the week was I born on?
The result panel names it, worked out from the birth date itself, so it is right back through the whole Gregorian calendar including the leap years.