What this calculator does
The Korean age system counts age differently from most of the world. A baby is considered 1 year old at birth, not 0, and every person’s age then rises by 1 together on 1 January, regardless of when their actual birthday falls. This calculator works out that Korean age from a date of birth and shows how many years it currently differs from your ordinary (international) age.
The gap between the two ages is not always the same 1 year people expect. Someone born late in the year can be 2 Korean years older than their international age for the first few weeks of a new year, until their actual birthday catches up. Enter a date of birth below to see both figures and the exact difference right now.
The formula
Korean age is the current year minus the birth year, plus 1. It ignores the month and day of birth entirely: only which calendar years have passed matters, and everyone’s Korean age changes on the same day, 1 January, rather than on individual birthdays. International age, shown alongside for comparison, is the ordinary age most countries use: it rises by exactly 1 on each birthday.
| Term | Meaning |
|---|---|
| Korean age | The traditional counting age: (reference year − birth year) + 1. A newborn starts at 1, and everyone gains a year together on 1 January. |
| International age | The ordinary age used in most countries and now also in South Korean law and medicine: it increases by 1 on each individual birthday. |
| Counting year | A Korean calendar year during which a person’s age is fixed, running from 1 January to 31 December regardless of birth date. |
The inputs explained
| Field | What to enter |
|---|---|
| Date of birth | The date of birth to calculate Korean age from. |
| Age as of this date | The date to calculate the age as of. Defaults to today. |
When to use it
Understanding a Korean age mentioned in conversation, film or a profile
Korean media, dramas and everyday conversation in Korea often state age using this system, which can be a year or two higher than the age westerners would assume from a birth year alone.
Working out why the difference is sometimes 2 years, not 1
Anyone born in November or December is still only their international age minus 1 for most of the following year, but their Korean age has already jumped twice: once at birth and once on the next 1 January. This calculator shows exactly when that 2 year gap narrows back to 1.
Comparing to the age used on official South Korean documents today
Since June 2023, South Korea has legally standardised on international age for most official, medical and legal purposes, so the traditional Korean age shown here is now mainly a cultural and conversational figure rather than a legal one.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How the gap changes before and after a mid-year birthday
The same person, born in the middle of the year, checked on several dates either side of their birthday.
| Date checked | Korean age | International (western) age | Difference |
|---|---|---|---|
| 1 Jan 2026 | 37 years old | 35 years, 6 months, 17 days | 2 years |
| 1 Mar 2026 | 37 years old | 35 years, 8 months, 14 days | 2 years |
| 14 Jun 2026 | 37 years old | 35 years, 11 months, 30 days | 2 years |
| 15 Jun 2026 | 37 years old | 36 years, 0 months, 0 days | 1 years |
| 1 Sep 2026 | 37 years old | 36 years, 2 months, 17 days | 1 years |
| 31 Dec 2026 | 37 years old | 36 years, 6 months, 16 days | 1 years |
The same pattern with a late-year birthday
A birthday falling right at the end of the year, so the 2 year gap this time only opens up for a short window in late December before closing again.
| Date checked | Korean age | International (western) age | Difference |
|---|---|---|---|
| 24 Dec 2025 | 36 years old | 34 years, 11 months, 29 days | 2 years |
| 26 Dec 2025 | 36 years old | 35 years, 0 months, 1 days | 1 years |
| 1 Jan 2026 | 37 years old | 35 years, 0 months, 7 days | 2 years |
| 1 Jun 2026 | 37 years old | 35 years, 5 months, 7 days | 2 years |
| 24 Dec 2026 | 37 years old | 35 years, 11 months, 29 days | 2 years |
| 26 Dec 2026 | 37 years old | 36 years, 0 months, 1 days | 1 years |
Questions
Why is Korean age sometimes 1 and sometimes 2 years more than international age?
It depends on whether the person’s birthday for the current international-age year has happened yet. Most of the year the gap is 1 year, since a baby starts at 1 rather than 0. In the window between 1 January and that year’s birthday, the gap widens to 2, because Korean age has already ticked over for the new year while international age is still waiting on the birthday.
Is Korean age still used officially in South Korea?
Not for most legal, administrative or medical purposes since a law change took effect in June 2023, which standardised those uses on international age. Korean age remains common in everyday speech, entertainment and casual context, but it is no longer the age used on official documents.
Does the traditional system use the lunar new year instead of 1 January?
An older, separate convention did tie the age change to the Lunar New Year rather than 1 January, and some sources still describe it that way. The commonly used modern version, and the one this calculator follows, resets on the solar calendar’s 1 January, which has been the standard reference point for decades.
What is the calculation if I do not know the exact birth date, only the year?
Korean age only depends on the birth year and the current year, not the month or day, so knowing just the birth year is enough to get the Korean age itself. A specific date of birth is only needed here to also show the international age and the exact size of the current gap between the two.
For the ordinary birthday-based age in years, months and days, see the age calculator. To count down to the next 1 January directly, see the New Year countdown calculator.