How to use
- Enter the date of birth.
- The second date defaults to today. Change it to find someone's age on any past or future date.
- Read the exact age in years, months and days.
- Check the countdown to the next birthday and the total number of days and weeks lived.
Why an exact age matters
For most everyday purposes “33 years old” is enough, but many situations need more precision. Eligibility rules for school entry, sports leagues, insurance and retirement plans often depend on the exact date someone reaches an age. Parents track a baby’s age in months and weeks, and some forms ask for age at a specific date rather than today. This calculator gives the full answer in years, months and days, plus a few related numbers.
How the calculation works
The number of full years is the difference between the two years, minus one if the birthday has not yet come around in the later year. The remaining months are counted from the most recent birthday, and the remaining days are whatever is left after those full months.
Month lengths vary, so a rule is needed for birthdays late in the month. When the target month does not have the same day, the last day of the month counts as completing the month. For example, from January 31 to February 29, 2024 is exactly one month.
All dates are handled as calendar dates, independent of your device’s time zone. Calculating at one minute to midnight, or while traveling abroad, will not shift the result by a day.
Leap-day birthdays
People born on February 29 only see their exact birthday once every four years. In common years this calculator moves the birthday to March 1, following the legal principle that a period ending on a day that does not exist ends on the last day of the month, so the new age starts the next day. The age in years is therefore unchanged on February 28 and increases on March 1.
Examples
Someone born on May 15, 1990 is 33 years, 11 months and 29 days old on May 14, 2024, and turns 34 the next day. On December 1, 2024 they are 12,619 days old, and their next birthday is 165 days away.
Other ways to count age
Some countries have traditionally used different systems. In South Korea, “counting age” started at one at birth and added a year every January 1, until the law standardized on international age in 2023. The Korean version of this page shows all three systems side by side.
Frequently asked questions
- How is exact age calculated?
- Subtract the birth year from the current year, then subtract one more if this year's birthday has not happened yet. The months and days are counted from the most recent birthday to the chosen date.
- When does someone born on February 29 have a birthday in other years?
- This calculator treats March 1 as the birthday in common years, which is the rule used in several legal systems, including England and Wales and South Korea. Some people celebrate on February 28 instead; legally the age changes when February ends.
- How are months counted when the birthday is on the 31st?
- When a month has no matching day, the last day of that month completes the month. Someone born on January 31 completes one month on February 28, or February 29 in a leap year.
- Why might another calculator give a different number of days?
- Some tools count the day of birth as day one, so they show one more day. This tool shows the number of days that have passed since birth, so a newborn is zero days old.
- Can I calculate age on a past or future date?
- Yes. Change the second date to find out how old someone was on their wedding day, or how old they will be on a future deadline.
- Is the birth date stored?
- No. The calculation happens in your browser and nothing is saved or sent anywhere.