How to use the age calculator
Enter the birth date and the date on which you want to measure age. The calculator counts completed calendar years first, then completed months, then remaining days.
Calendar age method
Age is counted in completed years, then completed months, then the remaining calendar days. If an anniversary falls on a day absent from the destination month, this model uses that month’s last day.
For example, January 31 to February 28, 2026 is one completed calendar month under this convention. A February 29 birthday uses February 28 as the anniversary in a non-leap year. Legal and institutional rules can differ.
Example: Emma checks age on a future date
Emma was born on January 15, 2000. On March 20, 2026, her calendar age is 26 years, 2 months, and 5 days.
The age-on date can be in the past or future. The calculation uses calendar anniversaries, with an anniversary clamped to the last day when a shorter month lacks the original day. It does not determine legal eligibility rules.
Choose the date on which you need the age
The default comparison is your device's current date. Change the age-on date to calculate age at a birthday, past event or future date.
The calculation uses calendar years and months, including leap years. For a month-end anniversary that does not exist in the target month, it uses that month's final day.
Calendar age and total days answer different questions
Calendar age counts completed years and months before the remaining days. Total elapsed days counts the day interval, including any leap days. Multiplying years by 365 does not reproduce that interval reliably.
For an age on a particular date, set the comparison date instead of using today. This is useful for a past record or a future milestone without changing the birth date.
Assumptions and limitations
What the estimate assumes
Local legal definitions of age at a specific instant or time zone can differ for edge cases around midnight.
Age Calculator FAQs
Does the calculator account for leap years?
Yes. It uses calendar dates rather than assuming every year has 365 days.
Can I calculate age on a past date?
Yes, as long as the selected date is not before the birth date.
Why can total days differ from years × 365?
Leap years and different month lengths make calendar time uneven.
Does this determine legal age?
It calculates calendar age. Legal rules can define timing or eligibility differently for specific purposes.
Why does an age calculator use calendar months instead of 30-day months?
Calendar months have different lengths, so exact calendar age is calculated from actual dates rather than assuming every month has 30 days.
Calendar-age calculation for general use. Legal eligibility rules may use their own definitions.