Age Calculator
Enter a date of birth to calculate age.
Exact age in years, months & days, plus fun stats and a birthday countdown | 100% Private
Correct calendar-aware borrowing logic handles month-end dates and leap years accurately.
Calculate age as of today, or any other date — great for eligibility checks and records.
See exactly how many days remain until the next birthday.
Total days, weeks, and months lived — fun numbers alongside the exact age.
Future birth dates, Feb 29 birthdays, and same-day calculations are all handled correctly.
All calculations run locally in your browser. Nothing is ever uploaded.
Calculating age sounds simple — just subtract the birth year from the current year — but getting the exact years, months, and days right requires careful calendar math. Our Age Calculator handles the tricky cases correctly: leap year birthdays, month-end dates, and same-day calculations.
We start with the raw calendar difference between the "as of" date and the birth date. If the "as of" day-of-month is smaller than the birth day-of-month (for example, born on the 28th, calculating as of the 5th), we borrow one month, adding the number of days in the calendar month immediately before the "as of" month. Similarly, if the "as of" month is earlier than the birth month, we borrow one year. This mirrors how humans naturally count age.
Because the borrowing logic always looks up the real number of days in the relevant calendar month (28 in a non-leap February, 29 in a leap February), a person born on February 29th gets a correct, sensible breakdown every year — not just once every four years.
We compute the difference between the birth date and the "as of" date using calendar-aware borrowing: if the "as of" day-of-month is earlier than the birth day-of-month, we borrow a month (adding the number of days in the previous calendar month) before subtracting, and similarly borrow a year if the "as of" month is earlier than the birth month.
The calculation uses real calendar month lengths, so a February 29th birth date is handled correctly in both leap and non-leap years — in non-leap years, the month-length borrowing correctly accounts for February only having 28 days.
The tool shows a clear error message and does not attempt to calculate a negative age.
Yes. The "Calculate age as of" field defaults to today's date but can be changed to any date on or after the birth date.
Besides the years/months/days breakdown, it shows total days lived, total complete weeks lived, and a countdown of days until the next birthday.