Age Calculator
The Age Calculator determines age from dates of birth and calculation dates. It is useful when you need an exact age rather than simply subtracting one year from another, because the month and day also affect whether a birthday has already occurred.
How to use this calculator
- Enter the date of birth.
- Enter the date on which you want to calculate the age, if the calculator provides a separate calculation date.
- Review the result in years and, where supported, the additional months and days.
- For official purposes, make sure the relevant date and local rules match the situation you are dealing with.
How age is calculated
Age is determined by comparing the birth date with the calculation date and checking whether the birthday has occurred in the current year.
- Simply subtracting birth years is not always sufficient. If the birthday has not occurred yet in the calculation year, the completed age is one year lower.
- For detailed age calculations, the calculator considers the month and day as well as the year.
- Calendar irregularities such as leap years can matter when working with exact dates.
Worked examples
Example: birthday already passed
If someone was born on March 10, 2000 and the calculation date is after March 10, 2026, their completed age is 26.
The person has reached their 26th birthday.
Example: birthday has not occurred
If the same person is evaluated before March 10, 2026, their completed age is still 25.
The person is 25 until their 26th birthday.
Understanding the result
Age in completed years changes on the birthday, not automatically on January 1.
An age stated in years is different from an exact duration of time since birth.
For legal age requirements, the applicable jurisdiction may define age in a specific way, so an online calculator should not replace official rules.
Important notes
Use the exact birth date when possible rather than estimating from the birth year.
For legal, immigration, identification, benefits, or eligibility decisions, verify the result against the relevant official requirements.
The calculator provides a date-based calculation and does not establish legal eligibility by itself.
Frequently asked questions
Why can my age be different from simply subtracting the years?
Because your birthday may not have occurred yet in the current year. An exact age calculation checks the month and day as well as the year.
Can I calculate my age on a future date?
Yes, if the calculator allows a separate calculation date. This can be useful for birthdays, eligibility dates, and future milestones.
Does an age calculator determine legal age?
It can calculate the age from the dates you provide, but legal definitions and eligibility rules can vary by jurisdiction and situation.
Related calculators
- Date Calculator — Add or subtract years, months, weeks, and days from any date.
- Date Difference Calculator — Find the exact number of days, months, and years between any two dates.
- Hours & Minutes Calculator — Add or subtract hours and minutes for work, study, travel, and everyday time calculations.
- Pregnancy Due Date Calculator — Estimate your pregnancy due date from your last menstrual period.
- Add & Subtract Time Calculator — Add or subtract hours and minutes to calculate a resulting time duration.
- Day of the Week Calculator — Find the weekday for any calendar date.
Related explanations
Learn the method behind the number or compare the terminology before using the calculator.
- How to Calculate Age from a Date of Birth — Learn how exact age is calculated using years, months, and days rather than a rough year difference.
- How to Calculate Days Between Dates — Learn how date intervals work, including leap years and inclusive vs exclusive day counting.
- Percent Difference — Understand percent difference, when it is appropriate, and how it differs from percentage change and percent error.
This page provides a calculation tool plus explanatory information so you can understand what the result means and when the underlying method may not fit your situation.