Age Calculator
Free age calculator from date of birth. See exact age in years, months, and days, plus total days, weeks, months, next birthday, and day of birth. Calendar-aware — not simple year subtraction. For date math utilities use Date Calculator.
How to Use the Age Calculator
Enter a date of birth and an optional calculation date to see exact age in years, months, and days, plus totals and next birthday details.
- Enter your date of birth.
- Select the date to calculate age on (defaults to today).
- Press Calculate.
- Review your age in years, months, and days.
- Check totals, next birthday, and day of birth in the details section.
Worked examples
- Born 2000-03-15, age on 2025-06-20: 25 years, 3 months, 5 days.
- Born today: 0 years, 0 months, 0 days.
- Born 2020-02-29, age on 2021-02-28: 1 year (Feb 29 uses Feb 28 in common years).
Common mistakes
- Using currentYear − birthYear before the birthday has occurred this year.
- Setting a calculation date before the date of birth.
- Confusing this with Date Calculator, which handles general date arithmetic.
Methodology
Age uses calendar-aware subtraction: full years since the last birthday anniversary, then remaining months and days — not currentYear − birthYear before the birthday. Totals count whole days between the birth date and the calculation date.
Limitations
Calendar-aware age only — not a substitute for legal age verification. Leap-day birthdays use February 28 in common years. For general date arithmetic (add/subtract days, working days), use Date Calculator.
Privacy
Dates stay in your browser. This calculator does not send birth dates to ToolsLibrary servers.
FAQ
How is age calculated?
Age uses calendar-aware subtraction: full years since the last birthday anniversary, then remaining months and days. It is not currentYear − birthYear before the birthday occurs.
Can I calculate age from date of birth?
Yes. Enter your date of birth and press Calculate. The default calculation date is today.
Can I calculate age on a specific date?
Yes. Change “Calculate age on” to any date on or after your birth date — past, today, or future.
Does the calculator account for leap years?
Yes. Leap years affect day counts and anniversary dates. February 29 birthdays use February 28 in common years for anniversary scheduling.
How are February 29 birthdays handled?
In non-leap years, the anniversary and next-birthday logic uses February 28 so age advances consistently on that date.
Can I calculate age in months and days?
Yes. Results include exact years/months/days plus total months, weeks, and days elapsed since birth.
Can I calculate age for a future date?
Yes. Set a future “Calculate age on” date to see how old someone will be on that date. Date of birth itself cannot be in the future.
What happens if the birth date is today?
Age is 0 years, 0 months, and 0 days. Next birthday is one year from today.
How accurate is the calculation?
The engine uses calendar dates (not simple year difference) and counts whole days between dates for totals. It is suitable for everyday age-from-birth calculations.
What is the difference between Age Calculator and Date Calculator?
Age Calculator focuses on a person’s age from date of birth with birthday context. Date Calculator handles general date math: add/subtract days, working days, week numbers, and more.