Age Calculator
Calculate your exact age in years, months and days from your date of birth, plus your age in months, weeks and days and the date of your next birthday.
- In months
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- In weeks
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- In days
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How to use the age calculator
- Enter your Date of birth.
- Leave Age on set to today, or pick another date to find out how old someone was, or will be, on that day. The Today button puts the current date back.
- Read your exact Age in years, months and days, updated as you type.
- Check the totals In months, In weeks and In days, and the Next birthday with its weekday and how many days are left.
- If you were born on February 29, choose how your birthday is counted in common years: Celebrate on Feb 28 or Celebrate on Mar 1.
How the exact age is calculated
This tool counts calendar units, the same way people do in everyday life, rather than dividing a number of days by 365. First, it finds the most recent birthday on or before the reference date: that gives the number of completed years. Then it counts the whole months since that birthday, and finally the days left over.
For example, someone born on May 15, 1990 is 36 years, 4 months and 14 days old on September 29, 2026: their 36th birthday was May 15, 2026, four “monthly birthdays” followed (June 15 to September 15), and 14 days have passed since September 15.
The calculation works on dates only, not on clock times, so daylight saving time changes and your device’s time zone can never shift the result by a day. Leap years are taken into account: a year has 365 or 366 days, and a month has 28 to 31 days, depending on the calendar.
Birthdays at the end of the month and on February 29
Months don’t all have the same length, so some dates need a rule. When a month has no matching day, this tool uses its last day: a person born on January 31 completes their first month on February 28 (or 29 in a leap year).
People born on February 29 have a real birthday only in leap years. In the other years, customs and laws differ. Many people celebrate on February 28, which keeps the birthday in February. Others, and some legal systems (for instance in the United Kingdom and Hong Kong), consider that the person becomes one year older on March 1. The option Feb 29 birthdays in common years lets you choose either convention, and it changes both the age and the Next birthday date.
Your age in months, weeks and days
Besides the usual years-months-days format, the tool shows three totals:
- In months: the number of whole months since birth, handy for babies and toddlers, whose age is often given in months until about two years.
- In weeks: whole weeks plus the remaining days, the unit used for newborns and during pregnancy follow-ups.
- In days: the exact number of days you have lived, including every February 29 along the way. Many people like to celebrate their 10,000th day, which falls a little after age 27.
Frequently asked questions
How do I calculate my exact age?
Enter your date of birth: this tool compares it with today’s date and returns your age in completed years, months and days. To calculate your age on another day, change the Age on date.
Why is my age in days not simply years × 365?
Because leap years add an extra day about every four years, and the calculation counts the real calendar. Someone who is 40 has lived through about ten February 29s, so their age in days is around 14,610, not 14,600.
When does someone born on February 29 turn a year older?
In leap years, on February 29. In other years it depends on the convention you choose: on February 28 with Celebrate on Feb 28, or on March 1 with Celebrate on Mar 1. The official rule varies by country, so check local law when it matters, for example for a driving licence or retirement age.
Can I calculate someone's age at a date in the past or future?
Yes. Set Age on to any date after the date of birth, for example to find out how old a grandparent was at their wedding, or how old a child will be on the first day of school.
Is my date of birth sent anywhere?
No. The calculation runs entirely in your browser, and the dates you enter are never sent to a server or stored.
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