How age is calculated
This calculator uses the common age system where age increases on a person's birthday. Month and day output uses calendar months, so month-end cases can have reasonable alternative interpretations.
Example
Someone born on May 18, 2000 is 26 years old on May 18, 2026. On May 17, 2026, they are still 25 years old in the common birthday-based system.
Common mistakes
Check whether the use case needs completed years, exact days or an age on a future date. Different forms may ask for different formats.
How to use the result
The result shows age in years, months and days, plus total days, approximate weeks and months, next birthday and half birthday. That makes it useful for forms, eligibility checks, planning dates and quick comparisons without switching to a separate date calculator.
References
- NIST: UTC(NIST) Time Scale, accessed 2026-05-14.
Last reviewed: 2026-05-14