How age is calculated
International age starts at 0 on the day you're born and increases by one each birthday: this year minus your birth year, minus one if your birthday hasn't happened yet this year.
More detail
Korean age systems
Korea traditionally used “세는 나이” (counting age): you're 1 at birth and gain a year every New Year (this year − birth year + 1). “연 나이” (year age) ignores the birthday entirely (this year − birth year) and still applies to some age limits. International age is the birthday-based standard.
Note. Since June 2023, Korean law and administration use international age everywhere — so “age” means international age unless stated otherwise.
Frequently asked questions
How is international (만 나이) age calculated?
Take the current year minus your birth year. If your birthday hasn't happened yet this year, subtract one more. Someone born in 2000 turns 25 in 2025 after their birthday, but is still 24 before it.
What's the difference between 만 나이, 세는 나이, and 연 나이?
International age (만 나이) counts from 0 and adds a year on each birthday — the legal standard since June 2023. Korean age (세는 나이) starts at 1 at birth and adds a year every New Year's Day, so it can run 1–2 years ahead. Year age (연 나이) is simply this year minus birth year, ignoring the birthday.
Why is my Korean age 1–2 years ahead of my international age?
세는 나이 counts the birth year as age 1, and everyone gains a year on January 1 regardless of their actual birthday. A baby born in December is already “2 years old” in 세는 나이 within weeks, while their 만 나이 is still 0.
How many days until my next birthday?
Enter your date of birth above — the Next birthday output counts the days from today to your next birthday, or shows “Today!” if it's today.