How does this calculator work?
Enter a birth date and a comparison date. The tool counts complete calendar years and months first, then any remaining days. When an anniversary falls on a missing day, such as February 29 in a non-leap year, it uses the final day of that month.
Quick example
Someone born on January 15, 2001 is 25 years old on January 15, 2026. Change the as-of date to calculate age in the past.