Everyday Life
Age Calculator
Enter a date of birth to get an exact age in years, months and days, plus the next birthday.
Any date from 1900 onwards
Defaults to today
Choose a date of birth to work out an exact age.
Free to use. No sign-up required.
How it works
Age is worked out using real calendar arithmetic, not by subtracting years. Whole years are counted first, then whole months, and finally the days left over.
This matters because months are different lengths. Counting from 31 January, one month lands on the last day of February, not on a date that does not exist. The calculator resolves the years and months first, then measures the remaining days from that point, so the day count is never negative.
Leap years are handled by the calendar itself. A span that crosses 29 February counts that day, so 1 January 2024 to 1 January 2025 is 366 days while the same span a year later is 365.
All dates are treated as calendar dates with no time zone attached, so the result will not shift depending on where you are or when daylight saving changes.
Formula
Exact age
whole years → whole months → remaining days
Resolved in that order from the date of birth to the target date.
Worked examples
Born 15 June 1990, as of 15 June 2025 → 35 years exactly
On the birthday itself the age is a whole number: 35 years, 0 months, 0 days.
Born 15 June 1990, as of 14 June 2025 → 34 years, 11 months, 30 days
One day before the birthday the age is still 34, with the next birthday one day away.
Born 15 January 2000, as of 10 March 2025 → 25 years, 1 month, 23 days
25 whole years to 15 January 2025, one whole month to 15 February, then 23 days to 10 March.
Frequently asked questions
How are leap years handled?
The calculation walks the real calendar, so 29 February is counted whenever it falls inside the span. There is no 365-day approximation anywhere in the result.
What happens to a 29 February birthday in a non-leap year?
The next birthday is shown as 1 March in years that have no 29 February. The age in years still increments on that date.
Can I calculate age as of a past or future date?
Yes. The "as of" date defaults to today but you can set it to any date after the date of birth, which is useful for eligibility cut-offs and application deadlines.
Why does the months figure sometimes look lower than expected?
A month only counts once the same day-of-month is reached. Counting from 31 January to 29 February gives 29 days rather than one month, because the 31st never occurs in February. This follows the same convention spreadsheets use.