Age calculator
The calculator reports completed age on a date you pick, not “age today.” That keeps the result in the page you can re-read, instead of depending on the clock.
Years, months, and days are calendar counts. The total is also given as an exact number of days, using UTC so a time zone cannot add or remove a day.
Calculator
Required fields are marked with *.
Use a comma or a dot for the decimal, as in 12.5 or 12,5. Type thousands as 1000 or 1 000. A single comma or dot is the decimal mark, so 1,000 means 1.
Results
The result will appear here.
How to use this calculator
- Enter the birth date. 29 February is accepted only in a leap year, because that is a real date.
- Enter the date you want the age for.
- Read the completed years first. The note appears when a 29 February birthday is moved.
Formula
A birthday counts when the anniversary has arrived. If someone is born on 29 February, a year with no 29 February uses 1 March as the birthday. On 28 February they are still a year younger. In a leap year the birthday stays on 29 February.
After the completed years, months advance the anniversary day and clamp to the last valid day of the month. The leftover is an exact day count. Because February is short, the day count just before a moved birthday can look long.
Worked example
Born 15 March 1990, age on 15 March 2026
The anniversary is the same month and day, so the age is 36 years, 0 months, and 0 days.
Someone born on 29 February 2000 is still 20 on 28 February 2021, and turns 21 on 1 March 2021.
36 years, 0 months, and 0 days.
Questions
Why 1 March and not 28 February?
On 28 February the February 29 anniversary has not happened yet. Treating 1 March as the birthday means the age increases on the first day that exists after the missing date.
Is this a legal definition of age?
No. Some laws use a different convention. This page states its own rule so the number is predictable.
What if the target date is the birthday?
The completed age increases on that day. The months and days are then zero if the anniversary matches exactly.
Sources
Last reviewed November 1, 2026