Age Calculator

An age calculator is an online tool that works out how old someone is, in whole years, months and days, from a date of birth and a second date, which is today unless you choose another day. It counts full calendar years first, then the remaining full months, then the leftover days, which is how age is normally stated. Dividing the total number of days by 365 gives a slightly different answer, because leap years add an extra day. For example, someone born on 15 March 2000 is, on 10 October 2026, 26 years, 6 months and 25 days old. The calculator also shows the same span as totals in months, weeks and days, and the number of days until the next birthday. Everything is calculated in your browser, so the date of birth you enter is not sent to us or stored.

The calculator counts full calendar years first, then the remaining full months and days. This is the way age is normally stated, rather than dividing the days by 365.

The totals in months, weeks and days are shown as well, for example for forms that ask for age in months.

Take a person born on 14 August 1992 and ask for their age on 3 March 2025. Counting full calendar years first, 14 August 2024 is the last birthday before that date, so the age is 32 years. From 14 August 2024, six full months bring us to 14 February 2025. The remaining stretch from 14 February to 3 March is 17 days, because February 2025 has 28 days: 14 days to the end of February plus 3 days into March. The result is 32 years, 6 months and 17 days.

The same span can be stated in other units. It is 390 full months (32 times 12, plus 6), 1,698 full weeks and 11,889 days in total. The next birthday is 14 August 2025, which is 164 days after 3 March 2025. Dividing 11,889 days by 365 would give about 32.57 years, which is not the same as 32 years and 6 months, because 32 years contain eight leap days. This is why the calculator counts calendar years, months and days instead.

A leap year adds 29 February to the calendar, so a person born on that day has a real birthday only once every four years. Leap years are normally the years divisible by 4, except century years that are not divisible by 400, so 2000 and 2024 are leap years while 1900 and 2100 are not.

Here is what this calculator does for a date of birth of 29 February 2000. Counting months, it moves the birth date forward by whole months and, when the target month is shorter, uses the last day of that month instead. In 2025 that anchor is 28 February, so on 1 March 2025 the result is 25 years, 0 months and 1 day, and on 28 February 2025 it is 24 years, 11 months and 30 days. The countdown to the next birthday follows the same logic and treats 1 March as the birthday in years without a 29 February: on 28 February 2025 it shows 1 day. In a leap year such as 2024, 29 February itself is the birthday and the result on that day is exactly 24 years.

Rules for 29 February birthdays differ between organisations and countries, and some treat 28 February and others 1 March as the birthday in common years. If a form or contract defines its own rule, follow that rule and use the calculator only as a cross-check.

An exact age helps when a date matters more than a rounded number: checking how old someone is on a deadline, an application date or the first day of a school year, comparing the age of two children on the same day, or filling in a form that asks for age in months. Set the second date to the day in question and read the result. The calculator reports the arithmetic only and cannot say whether a person meets a legal or contractual requirement, so check the exact wording of the rule that applies to you.

To count the days between two dates that are not birthdays, or to add or subtract days from a date, use the [Days Calculator](days-calculator).