Wraplet guide
How to Calculate Age in Years, Months, and Days
Learn how age is calculated from a date of birth, including completed years, months, days, and leap-year edge cases.
The basic method
Age is the difference between a birth date and a comparison date. The cleanest result counts completed calendar years first, then completed months, then remaining days.
For example, someone born on 2000-01-01 is 26 years, 5 months, and 26 days old on 2026-06-27.
Formula
Age = comparison date - date of birth.
If the comparison day is earlier than the birth day, borrow days from the previous month. If the comparison month is earlier than the birth month, borrow one year.
Frequently asked questions
Why do age calculators show months and days?
Years alone hide the remaining time after the last birthday. Months and days make the result exact for forms, school age, and personal dates.
Do leap years change the result?
Leap years can affect total days, but completed calendar years and months are still counted from the birth date to the comparison date.