Age Calculator
Calculate an exact age in years, months and days from a date of birth, with total days, weeks and the next birthday. Leap years handled correctly.
Defaults to today.
How it works
- Enter a date of birth.
- Optionally change the target date to calculate an age at a past or future date.
- The result updates as you type, in years, months and days plus exact totals.
Frequently Asked Questions
How is the age calculated?
By counting whole months from the date of birth and then the remaining days, rather than subtracting years. Simply subtracting the years is wrong for anyone whose birthday has not yet arrived this year — a very common bug in age calculators.
What about a 29 February birthday?
In leap years the anniversary is 29 February; in common years it is treated as 1 March, the convention most jurisdictions use for legal age. The tool states which rule it applied.
Why does 31 January to 1 March give 1 month and 1 day?
Because one month after 31 January is the end of February, and 1 March is one day after that. Months have different lengths, so the calculation anchors to a real date instead of borrowing an arbitrary month length.
Can I calculate an age at a past or future date?
Yes. The target date defaults to today but can be set to any date on or after the date of birth.