Age Calculator
Calculate exact age in years, months, and days from a date of birth, with the next birthday and the day of the week you were born.
How to calculate your age
- 1
Enter the date of birth
Pick the date of birth in the first field.
- 2
Choose the date to measure on
The second field defaults to today. Change it to see the age on another date.
- 3
Read the results
Age in years, months, and days appears at once, with the next birthday, the weekday of birth, and totals in days, weeks, and months.
How age is calculated
Years, months, days
Age in years is the number of birthdays that have passed. The months are counted from the last birthday, and the days from the last month mark. Someone born on December 25, 1990 is 34 years, 9 months, 6 days old on October 1, 2025: 34 birthdays, then Dec 25 to Sep 25 is 9 months, then 6 more days. Age goes up on the birthday itself, not the day after.
Short months and leap days
When a month has no matching day, the count rolls to the 1st of the next month. A baby born on January 31 turns 1 month old on March 1 in a common year. A person born on February 29, 2000 turns 25 on March 1, 2025, and celebrates on February 29 again in 2028.
Korean ages
Counting age (세는 나이) is 1 at birth and adds a year every January 1, so a baby born on December 31 is 2 the next day. Year age (연 나이) is the current year minus the birth year. Since June 28, 2023, Korean law uses international age (만 나이) by default. Year age is still used for buying alcohol and tobacco under the Youth Protection Act and for military service.