Age Calculator
Calculate exact age in years, months, and days from a date of birth. Also shows the number of days until your next birthday.
Age
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Next birthday
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Figuring out someone's exact age in years, months, and days is trickier than it looks once you account for varying month lengths and leap years. This calculator does the date math for you: enter a date of birth and, optionally, a date to calculate the age as of, and it returns the precise age breakdown along with a countdown to the next birthday.
How to use this calculator
- Enter the date of birth in the date field.
- By default, age is calculated as of today's date — optionally enter a different 'as of' date to calculate age on a specific day.
- The result updates instantly and shows the age in years, months, and days, plus the days remaining until the next birthday.
How age is calculated
Age in years, months, and days is calculated by finding the difference between the date of birth and the target date, then breaking that difference down calendar-aware: full years are counted first, then the remaining months, then the remaining days — accounting for different month lengths and leap years along the way.
This is more accurate than simply dividing the total number of days by 365, which can be off by a day or more depending on how many leap years fall within the range.
Example: Calculating exact age
Date of birth: March 15, 2000. Calculating as of June 21, 2026.
Result: 26 years, 3 months, 6 days.
Example: Leap year birthday
Someone born on February 29, 2000 (a leap day) calculates their age the same way — in non-leap years, their birthday is typically observed on either February 28 or March 1, but the exact day-count math still applies correctly.
Frequently asked questions
How is age calculated in years, months, and days?
The calculator counts the number of complete years between the date of birth and today, then the number of complete months remaining, then the number of days remaining — adjusting automatically for different month lengths and leap years.
Does this calculator account for leap years?
Yes. The date math correctly accounts for leap years (including February 29) when calculating the precise number of days between two dates.
Can I calculate age as of a future or past date instead of today?
Yes. Enter a custom 'as of' date instead of using today's date — useful for legal, eligibility, or historical age calculations.
What happens if someone is born on February 29?
Their exact birthday only occurs in leap years. In non-leap years, this calculator still computes the correct age in years, months, and days based on the actual calendar dates.
How many days until my next birthday?
The calculator automatically shows the number of days remaining until your next birthday based on the date of birth you entered and the current date.