Age Calculator
Calculate exact age in years, months, and days. See total days, weeks, hours, and the countdown to the next birthday.
How Age is Calculated
Age is calculated by counting complete calendar years, then remaining complete months, then remaining days — matching the way birthdays work in everyday life. For example, someone born on Jan 31 who reaches Feb 28 in a non-leap year is considered 28 days older, not one month.
The "as of" date defaults to today but can be set to any future or past date — useful for calculating ages at specific historical moments or for checking whether someone will be old enough by a deadline.
Common Use Cases
- Eligibility checks — retirement age, voting age, driving age
- Medical — patient age at a specific visit date
- Legal — age at the time of an event or contract signing
- Historical — how old was a person on a historical date?
- Fun — count down days until a milestone birthday
Leap Years & Edge Cases
People born on February 29 (leap day) have their birthday recognized on Feb 28 in non-leap years by most legal systems, though some countries use March 1. This tool calculates next birthday using the actual date — Feb 29 will only match in leap years.
All dates are processed in your local timezone to avoid off-by-one errors that arise from UTC midnight conversions.
Frequently Asked Questions
Why does the age differ from what I expected?
Age is exact — it counts complete units. If your birthday is tomorrow, you have not yet turned that age. If you want approximate age in decimal years, divide total days by 365.25.
Can I calculate age for a future date of birth?
The date of birth must be on or before the "as of" date. The "as of" date can be set to any future date — useful for checking how old someone will be on a future deadline.
How accurate is the total hours/minutes count?
Hours and minutes are calculated from complete days only. They do not account for the exact time of birth since only the birth date (not time) is entered — so treat them as approximations.
Is any data sent to a server?
No — all calculations run entirely in your browser using JavaScript. The date of birth you enter never leaves your device.