Age Calculator
Enter a date of birth to get an exact age in years, months and days, the same age expressed in total days, weeks, hours and minutes, and the number of days until the next birthday.
How exact age is calculated
Age is a calendar interval, not a single number. The standard method counts complete years first, then complete months inside the remainder, then the leftover days.
When the day number is smaller than the birth day, one month is borrowed and the length of the previous month is added — which is why the same birth date splits differently in February and in a 31-day month.
Why two calculators disagree
There are two conventions for the leftover days. The completed-period method used here reports only fully elapsed units, so a baby born on 31 January is “0 months, 28 days” old on 28 February. Some calculators report “1 month” because the day number has been reached.
For official forms — visas, school cut-offs, retirement — use the definition published by the authority asking. This tool follows the completed-period convention, the same one used by ISO 8601 durations.
Frequently asked questions
How do I calculate my age in days?
Subtract your date of birth from today. The calculator shows that figure as Total days, with weeks, hours and minutes derived from it.
Why does my age in months and days change with the month?
Months differ in length. The split borrows days from the previous calendar month, so the same birth date gives a different day count in February than in a 31-day month.
How is age handled for someone born on 29 February?
In non-leap years the birthday countdown targets 29 February of the next leap year, while completed years still increase on 1 March. Legal definitions vary by country.
Can I calculate age at a future date?
Yes. Set the second field to any date — a retirement date or an exam cut-off — and the tool reports the age on that day.