Age Calculator

You only need a date of birth. The rest is optional.

1. Enter the date of birth. This is the only required field.
2. Choose a "calculate age as of" date if you want one. Leave it empty and the calculator uses today's date. Fill it in to get the age on any past or future day.
3. Read the result. You get the exact age in years, months and days, plus the total months and total days lived.

A worked example

Say someone was born on 15 March 1990 and you want their age as of 13 October 2026. The result is 36 years, 6 months and 28 days. That is 438 months in total, or 13,361 days.

Once you know an exact age, you might want to put it to use. Our BMI calculator is a quick next step for a general health check.

The calculator uses calendar subtraction, the same way you would do it on paper. It works out full years first, then full months, then the leftover days.

The tricky part is when a part of the later date is smaller than the matching part of the birth date. In that case you borrow.

Borrowing, step by step

Take 13 October 2026 minus 15 March 1990:

• Days: 13 is less than 15, so borrow the length of the previous month. September has 30 days, so 13 + 30 = 43, and 43 − 15 = 28 days. October now counts as September, so the month number drops by one.
• Months: September (month 9) minus March (month 3) leaves 6 months. If this had come out negative, we would borrow 12 months from the year.
• Years: 2026 − 1990 = 36 years.

Result: 36 years, 6 months, 28 days.

Why not just divide total days by 30?

Because months are not all 30 days long. They run from 28 to 31. Dividing 13,361 days by 30 gives about 445 months, which is wrong. The real figure is 438. Small errors add up over a lifetime, and the leftover days would be wrong too.

Leap years are handled exactly. Every 29 February that falls between the two dates is counted as a real day.

Eligibility cutoffs. Schools, sports leagues and employers often ask for your age on a fixed date, such as 1 September or 31 December. Enter your date of birth and that cutoff date to see if you qualify, and by how many days you made it or missed it.

Historical ages. How old was your grandmother when she moved abroad? How old was a founder when the company launched? Enter the birth date and the date of the event to get the exact answer in years, months and days. This is also useful for family trees and school projects.

Future milestones. Want to know how old you will be on a wedding day, a retirement date or a trip? Set a future date to find out. To find when you turn 18, 30 or 60, add that many years to the birth date and use that date as the "as of" date. If you are tracking health goals along the way, our body mass index tool can sit alongside it.

Born on 29 February

Leap-day birthdays only come around once every four years. In other years, people mark the day on 28 February or 1 March, and legal rules differ by country and by purpose, such as driving or voting age. This calculator treats 1 March as the birthday in non-leap years — for example, someone born 29 February 2000 turns 25 on 1 March 2025.

East Asian traditional age

In some traditional East Asian systems, a newborn counts as age 1 at birth and gains a year at the lunar or calendar new year. That can make someone one or two years older than their Western age. This calculator shows the standard (international) age only.

Weekday of birth

The calculator does not show the weekday of a birth date, but it is a fun thing to look up. The 15 March 1990 example was a Thursday. The Gregorian calendar repeats on a long cycle, so the weekday is easy to work out once you know the rules (see the Gregorian calendar overview).