Age Calculator
Enter your date of birth to see your exact age in years, months and days, plus the total number of days you have lived.
Quick answer. Age is calculated by subtracting the birth date from today's date, year by year, month by month and day by day, then borrowing from the previous month where needed.
How the age is calculated
The calculator subtracts the birth date from today's date year by year, month by month and day by day.
When the day count goes below zero, it borrows the number of days in the previous month. When the month count goes below zero, it borrows 12 months from the year.
Worked example
Birth date is 15 March 1990. Calculation date is 8 October 2026.
Years are 36. Months are 7, but the day count is minus 7, so one month is borrowed and September's 30 days are added. Result: 6 months and 23 days.
Total days lived is 13,356.
Common mistakes
Entering a date in the wrong order. Use the calendar date of birth as printed on your records.
Expecting the age to change at a specific hour. The calculator compares calendar dates only.
Leap years
A leap year has 366 days. The extra day falls on 29 February. Leap years occur in years divisible by 4, except years divisible by 100 that are not divisible by 400.
The calculator follows the Gregorian calendar, so day counts include every leap day between the two dates.
Birthdays on 29 February
The calculator counts calendar dates. A person born on 29 February has a birthday in leap years only. Many countries treat 1 March as the legal birthday in other years, so check your local rule if you need it for a document.
Using the total days figure
The total days figure is useful for planning, for example counting days until a milestone. It counts whole days, not hours, so the result does not change during the day.
Questions
Does it accept future dates?
No. The date of birth must be today or earlier.
Does my time zone change the result?
No. The calculator compares calendar dates, so the time of day does not change the result.
How do I find my age in days?
Enter your date of birth. The total days lived figure is shown with your years, months and days.
Last updated: 2026-10-08. Calendar arithmetic using the Gregorian calendar. Calendar method checked against worked examples.