Age calculator
Enter a date of birth to get the exact age in years, months and days, the total months, weeks and days lived, and how long until the next birthday.
- Free
- No sign-up
- In your browser
Today by default. Change it to calculate age on another date.
Exact age
Pick a date of birth to see the age.
How to use this tool
- Pick the date of birth in the first field.
- Leave the reference date as today, or change it to find out how old someone was (or will be) on another date.
- Check the exact age, the totals in months, weeks and days, the days until the next birthday and the weekday of birth.
- Press “Copy” to take the exact age with you, or “Today” to use the current date as the reference again.
How exact age is calculated
First, complete years are counted: a year is completed each time the same day and month as the birth date comes around. Then the complete months since the last birthday, and finally the days left over since the last “monthiversary”.
For example, someone born on May 15, 1990 is, on September 24, 2026, 36 years old (reached on May 15, 2026), plus 4 months (reached on September 15) and 9 days.
Months of different lengths and month ends
Because months have 28, 29, 30 or 31 days, “one month” isn't a fixed number of days. This calculator treats a month as complete when the same day number comes around in the next month, or the last day of that month if that day doesn't exist. So from January 31 to February 28, 2023 is exactly 1 month, while in 2024, a leap year, the month is completed on February 29.
That's why the totals in days and weeks are always exact, while months depend on the actual calendar. Other tools may follow slightly different conventions for month-end dates and give a result that's one day off.
Born on February 29
People born on February 29 only have their exact birthday in leap years. In other years, this calculator treats February 28, the last day of February, as their birthday.
It's not the only convention: some systems and laws use March 1 instead. If you need the date for a legal purpose, check the rules that apply in your state or country.
Leap years
A year is a leap year if it's divisible by 4, except for years divisible by 100 that aren't divisible by 400. That's why 2000 and 2024 were leap years but 1900 wasn't. The calculator takes these years into account when counting days.
Examples
Born May 15, 1990, as of September 24, 2026
Age: 36 years, 4 months and 9 days. In total, 436 months and 13,281 days. Born on a Tuesday.
Born January 1, 2000, as of September 24, 2026
Age: 26 years, 8 months and 23 days, which is 9,763 days or 1,394 weeks and 5 days. January 1, 2000 was a Saturday.
Born February 29, 2000
With February 28, 2027 as the reference date, the calculator shows exactly 27 years and a note that it's their birthday. The next one, February 29, 2028, falls in a leap year.
Frequently asked questions
Can I calculate how old someone will be on a future date?
Yes. Change the reference date to the future date you're interested in to see the age on that day. It also works to find out how old someone was on a past date.
Why does another calculator give me a one-day difference?
Usually it's down to how months are counted when the birth day doesn't exist in the reference month (for example, the 31st in a 30-day month), or whether the end date is included. This calculator doesn't count the day of birth as a day lived: on the day you're born, you're 0 days old.
Does it account for leap years?
Yes. All calculations use the Gregorian calendar with its leap years, so the totals in days and weeks are exact.
What if the date of birth is after the reference date?
The calculator will tell you that the date of birth can't be after the reference date and won't show a result until you fix it.
Is my data sent to a server?
No. All calculations happen in your browser and the date of birth you enter isn't sent to any server.
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