Age calculator

How to use it

1. Enter the date of birth. Pick the day in the calendar or type it in the field. Any date from 1900 onwards works.
2. Choose the date to measure to. It is today unless you change it. Set another day to see the age on a deadline, the first day of school or a future anniversary.
3. Read and copy the result. The big figure is the age in completed years, with the extra months and days below. The boxes show the totals and the next birthday; the copy button puts the age on your clipboard.

How exact age is calculated

Age in completed years goes up by one on each birthday. To add months and days, the calculator starts from the date of birth, counts the whole years, then the whole months left over, and finally the remaining days. It is the same reasoning you would follow with a wall calendar.

Months have different lengths, so «one month» is not a fixed number of days. If you were born on the 31st, in shorter months the month ends on the last day available: April 30, February 28 or 29. That is why two people with the same gap in days can show slightly different ages in months.

The totals are plain counts: days lived are the difference between the two dates, weeks are the days divided by 7, and months are the years times 12 plus the extra months. For the gap between any two dates, not just an age, use the date calculator.

Birthdays on February 29

People born on February 29 only get their real birthday in leap years. In common years this calculator counts the birthday on February 28, the last day of the month, which is how the Italian and Romanian civil codes, for example, handle a period that ends on a day the month does not have.

Rules for legal age are not the same everywhere. Some jurisdictions and agencies treat March 1 as the birthday in common years. When age has legal effect, for a driving licence, a benefit or a contract, check the rule used by the authority involved.

Worked examples

When the exact age matters

• Applications and eligibility: age limits are usually checked on a set date, such as the closing date. Enter that date as the reference.
• School and sports: enrollment often depends on the age reached by a cut-off day.
• Babies and toddlers: in the first years age is given in weeks or months, and the totals have them ready.
• Milestones: 10,000 days old, 1,000 weeks, a round birthday. With a future reference date you can see how old you will be on any day.

To count down the days to a birthday or any other date, try how many days until.

Sources

• Gregorian calendar leap-year rule: every 4 years, except century years not divisible by 400.
• UK Family Law Reform Act 1969, section 9: a person attains a given age at the start of the relevant anniversary of the date of birth.
• Italian Civil Code, art. 2963, and Romanian Civil Code, art. 2552: a period counted in months or years that would end on a missing day ends on the last day of the month.

Sources checked on 14/10/2026. This is a calendar calculation and does not replace the rules of the office that assesses your age.

Frequently asked questions