Age Calculator
Exact age in years, months and days — plus your next birthday countdown.
Free · No sign-up · Runs locally in your browser · Also available in Chinese (中文)
What is Age Calculator?
An age calculator measures the precise interval between a birth date and any target date, expressed the way humans say it: years, months and days. Simple subtraction fails here because months have different lengths, so the tool applies calendar-aware arithmetic instead.
Beyond the headline age, it also reports totals — days lived, weeks, hours — and the countdown to the next birthday, which makes it handy for planning milestones, checking legal age requirements or settling friendly arguments about who is older.
How to use it
- 1Enter the birth date (year, month, day).
- 2Optionally set a target date; it defaults to today.
- 3Read the exact age in years, months and days.
- 4Check the totals row for days, weeks and hours lived, and the next-birthday countdown.
Common use cases
- Filling in official forms that require age in completed years and months.
- Parents tracking a baby's age in weeks and months against development milestones.
- Planning milestone birthdays and seeing exactly how many days remain.
Frequently asked questions
▸How are months counted when lengths differ?
The tool follows the standard convention: whole months are counted first, and leftover days are computed against the actual lengths of the months involved, so Feb 28 to Mar 31 is one month and three days.
▸Does it account for leap years?
Yes. All arithmetic is done on the real calendar, so ages spanning leap years — including February 29 birthdays — are counted correctly.