How to Use
- Enter your date of birth
Input your birth date using the year, month, and day fields.
- Select the target date
Choose the date you want to calculate your age as of. The default is today's date.
- View results
Click the Calculate button to see your exact age in years, months, and days.
What is age? International, year-based, and counting age
Age is the amount of time, expressed in years, that has passed from birth to a given reference date. For the same person, the number shown can differ depending on the counting method, which is why three different age systems have traditionally been used in Korea.
Three types of age
- International age: The global standard, where you gain one year on each birthday. The day you are born, you are 0 years old.
- Year-based age: The current year minus the birth year. It is used as the standard in some laws, such as those on military service and youth protection.
- Counting age: The traditional method, where you are 1 at birth and gain a year every January 1.
With the Unified Age Act that took effect on June 28, 2023, age in administrative, legal, and contractual contexts has been standardized to international age. This calculator shows international age by default and provides year-based and counting age for reference.
Calculation formula
International age depends on whether your birthday has passed.
International age = (reference year - birth year) - (1 if birthday not yet passed, 0 if passed)
Example: As of June 3, 2026, someone born September 20, 1998 has not yet reached this year's birthday (9/20), so (2026 - 1998) - 1 = 27 years.
- Year-based age = reference year - birth year = 2026 - 1998 = 28
- Counting age = (reference year - birth year) + 1 = 29
- Zodiac = birth year % 12 mapped to the 12 animals (1998 % 12 = 2 -> Tiger)
- D-day = next birthday date - reference date (in days)