Age Calculator

How to use the age calculator

1. Pick the date of birth in the first field. Any date from January 1, 1800, onward works.
2. Leave age on set to today, or choose another date, for example the start of a school year, a retirement date or a past anniversary.
3. Read the result: the age in years, months and days at the top, followed by the totals, the date of the next birthday, how many days are left until it and the weekday of birth.

The second date can't be earlier than the date of birth. If it is, the calculator asks you to fix it.

How the age is calculated

The calculator works with calendar dates only, with no time of day or time zone, so the result is the same wherever you are.

1. Years, months, days: it subtracts the birth year, month and day from the year, month and day of the second date. If the days come out negative, it borrows one month and adds the length of the month just before the second date (28, 29, 30 or 31 days). If your birth day doesn't exist in that month (say the 31st), the month is counted from its last day instead, so the days never go negative. If the months come out negative, it borrows one year and adds 12 months.
2. Total days is the exact number of days between the two dates. Total weeks is that number divided by 7, rounded down. Total months is years × 12 + months.
3. Next birthday is the next time the birth month and day come around after the second date. If the second date is the birthday itself, the countdown shows the following year.

Leap years and February 29

The Gregorian calendar, the civil calendar used in the United States, has a leap year every year divisible by 4, except century years, which are leap years only when divisible by 400. So 2000 was a leap year, but 1900 was not. People born on February 29 have a real birthday only in leap years. In other years the calculator shows February 28 as the birthday. That is a common convention, not a legal rule: some people celebrate on March 1 instead.

Age calculator examples

Born May 15, 1990, age on October 12, 2026

The day count is 12 − 15, which is negative, so the calculator borrows September's 30 days: 12 + 30 − 15 = 27 days, and the months drop from 5 to 4. The age is 36 years, 4 months and 27 days. That is 13,299 days, 1,899 full weeks or 436 months. The next birthday is Saturday, May 15, 2027, in 215 days, and the person was born on a Tuesday.

Leap-day birthday: February 29, 2000, age on January 10, 2027

The age is 26 years, 10 months and 12 days, or 9,812 days. Because 2027 is not a leap year, the next birthday is shown as Sunday, February 28, 2027, which is 49 days away.

A child born August 3, 2019, age on October 12, 2026

The child is 7 years, 2 months and 9 days old: 2,627 days, 375 weeks or 86 months. They were born on a Saturday, and the next birthday, August 3, 2027, is 295 days away.

Reading the result

• Completed units: years and months count only completed periods. Someone who is 36 years and 11 months old is still 36.
• Day borrowing: months have different lengths, so two people with the same total days can show slightly different month-and-day splits. The total in days is the unambiguous figure.
• Time of birth: hours are not considered. If you were born late in the evening, you are a few hours younger than the day count suggests.
• Official documents: eligibility for school, benefits or licenses follows the rules of the agency involved, which may set a cutoff date. Check those rules rather than relying on a day count.