Korean Age Calculator

Background.

This calculator gives you all three of the ages South Korea uses, side by side, from one birth date measured on one day. Enter a date of birth and the date you want the ages measured on, and it returns the traditional Korean counting age (세는 나이), the calendar-year age (연 나이), and the international age (만 나이) — plus the gap between the first and the last, and the one fact that decides that gap.

The reason there are three numbers rather than one is that Korea genuinely ran three systems at the same time for decades, and two of them are still in force. Traditional counting age makes you one year old the moment you are born, and everybody gains a year together on 1 January, which is why a baby born on 31 December is two years old the next day. Year age drops the 'one at birth' part but keeps the shared New Year increment: it is simply the current year minus your birth year. International age is what almost everyone outside Korea means by age — zero at birth, and one more on each birthday.

On 28 June 2023 the Age Counting Unification amendments took effect, and they settled which of the three the law means. Civil Act Article 158, wholly amended by Act No. 19098, now provides that a person's age 'shall be calculated based on his/her date of birth, incremented by one year on his/her birthday, and shown on a yearly basis'. General Act on Public Administration Article 7-2, added by Act No. 19148, says the same thing for administrative purposes: age is counted from the date of birth and expressed in years, 'except as provided in other statutes or regulations'. So unless a specific law says otherwise, an age written in a Korean statute, contract, hospital record or government form is the international age. The counting age this page shows as its headline number — because it is the number people actually ask for — carries no legal weight.

That 'except as provided' clause is doing real work, and it is why the year age is still on this page rather than treated as history. Two statutes that touch ordinary life kept it. The Youth Protection Act, which governs alcohol and tobacco sales, defines youth so that anyone who has reached 1 January of the year they turn 19 falls outside it — so the drinking threshold moves for a whole birth cohort on New Year's Day, not on each person's birthday. The Military Service Act runs conscription examinations and enlistment on the year count too, so everyone born in the same calendar year is called in the same year regardless of birth month. Elementary-school entry and the lower grades of the public-service examinations work the same way. If you are checking one of those thresholds, the number you want is the year age, not the international age and certainly not the counting age.

The gap between the counting age and the international age is always either one year or two, and which one it is depends on a single question: has the birthday arrived yet this year? Before it, the gap is two; on the birthday and after it, one. That is the whole of the arithmetic, and it is why two people can share an international age and differ by a year in Korean counting age — someone born in December 1994 and someone born in May 1995 are both 31 internationally in the middle of 2026, but 33 and 32 respectively in counting age.

Two scope points, both of which change how the numbers should be read. First, the date the ages are measured on is an input here, not your device's clock: all three counts change on 1 January, and a page that silently read the system time would give a different answer either side of a boundary you cannot see. Set it to today's date for the live answer. Second, the counting age here increments on 1 January. Historically it was tied to Seollal, the lunar new year, which falls in late January or February; that version needs a lunisolar calendar table this calculator does not have and will not guess at, so the solar convention — the one the Korean government's own explainer uses — is what is implemented.

What is korean age calculator?

Korean age is not one thing. '세는 나이' (sen-eun na-i, 'counting age') is the traditional East Asian reckoning: a newborn is one, and everyone advances together on New Year's Day, giving the formula current year − birth year + 1. '연 나이' (yeon na-i, 'year age') is the administrative shorthand that keeps the shared New Year increment but starts from zero: current year − birth year. '만 나이' (man na-i, 'full age') is the international count — completed years since the birth date, advancing on each individual's birthday. The three can produce three different numbers for the same person on the same day, and the spread between the highest and the lowest is always exactly two years for anyone whose birthday has not yet come round, and one year for anyone whose has. Korea's Age Counting Unification amendments of 27 December 2022, in force since 28 June 2023, made 만 나이 the default reading of 'age' throughout the statute book and in contracts and public documents, resolving decades of ambiguity — but they did not abolish the other two, and they left the year count expressly in place in the statutes that set the alcohol, tobacco and conscription thresholds.

How to use this calculator.

1. 01Enter the date of birth as ISO 8601 (YYYY-MM-DD). The year alone fixes the two Korean counts; the month and day decide only the international age.
2. 02Enter the date you want the ages measured on. Set it to today for the live answer, or to any other day to answer a hypothetical — 'how old was she when the law changed', for instance, using 2023-06-28.
3. 03Read the headline counting age (세는 나이) — that is the number a Korean speaker asking your age is asking for.
4. 04Read the international age (만 나이) for anything official: forms, contracts, hospital records, visa and residence-card applications. Since 28 June 2023 that is what 'age' means in Korean law by default.
5. 05Read the year age (연 나이) if you are checking alcohol, tobacco, conscription, school entry or a lower-grade public-service examination — those thresholds still move for a whole birth cohort on 1 January.
6. 06Check 'Birthday already this year?' to see why the gap is 1 or 2. Before the birthday the counting age runs two years ahead of the international one; from the birthday onward, one.

The formula.

Two of the three counts need nothing but the two years. The year age is the reference year minus the birth year, and the counting age is that plus one. Neither looks at the month or the day, which is exactly why both jump for everybody at once on 1 January. For the worked example below — born 31 December 1994, measured on 30 July 2026 — that gives 2026 − 1994 = 32 for the year age and 33 for the counting age, and it would give the same two numbers on any other day of 2026.

The international age is the one that needs the calendar. Start from the same subtraction, then take one more year off if the birthday has not yet arrived in the reference year. On 30 July 2026 a 31 December birthday has not arrived, so 32 − 1 = 31. That single subtraction is the entire difference between the international age and the year age, and it is why the gap between counting age and international age is 33 − 31 = 2 before the birthday and 1 from the birthday onward. The comparison is inclusive: on the birthday itself the birthday counts as arrived, so the age increments that day rather than the day after.

The comparison runs on the unrounded month-and-day pair, not on a rounded interval, and it runs against the anniversary as it falls in the reference year — which matters in exactly one case. For a birth date of 29 February there is no matching day in a common year, and Civil Act Article 160(3) supplies the answer for periods fixed by the year: 'if there is no corresponding day in the last month, the last day of the month shall be the day of maturity.' So a leap-day birthday matures on 28 February in a common year, and this calculator increments the international age that day. England and most US states reach the opposite answer and use 1 March. The divergence is one day, it appears only in common years, and the calculator says so beside the result when the birth date is 29 February.

Everything is anchored at UTC midnight on the proleptic Gregorian calendar, so no daylight-saving transition can push a birthday across a year boundary, and every figure is computed in arbitrary-precision decimal and rounded once at the end. All four numeric outputs are whole numbers by construction, so that rounding never changes an answer — it is a boundary formality, stated here so nobody has to guess.

A worked example.

Frequently asked questions.

References& sources.

1. [1]Korea Legislation Research Institute, Statutes of the Republic of Korea — CIVIL ACT (민법), English translation, current through Act No. 19098 of 27 Dec. 2022. Article 158 (Calculation and Showing of Age): 'The age of a person shall be calculated based on his/her date of birth, incremented by one year on his/her birthday, and shown on a yearly basis: Provided, That for a person whose first birthday has yet to come, his/her age may be shown on a monthly basis.' Article 160(3), relied on here for the 29 February anniversary: 'In cases where a period has been fixed by the month or year, if there is no corresponding day in the last month, the last day of the month shall be the day of maturity.' Retrieved 2026-07-30. The Korean text is the authoritative version.
2. [2]Korea Legislation Research Institute, Statutes of the Republic of Korea — GENERAL ACT ON PUBLIC ADMINISTRATION (행정기본법), English translation. Article 7-2, added by Act No. 19148 of 27 Dec. 2022: 'Except as provided in other statutes or regulations, the age for administrative purposes shall be calculated by including the date of birth and expressed in terms of years; provided, if a child has not reached the age of 1, his or her age may be indicated by the number of months.' Retrieved 2026-07-30.
3. [3]Republic of Korea, Government Policy Briefing (대한민국 정책브리핑, korea.kr) — '나이'로 인한 혼란 사라진다…'만 나이 통일'로 달라지는 것들. The official explanation of the 28 June 2023 enforcement date and of all three counts: 만 나이 as current year − birth year, less one more for a person whose birthday has not yet come; 연 나이 as current year − birth year regardless of birthday; and the note that the Youth Protection Act and the Military Service Act keep the year count. Retrieved 2026-07-30; Korean language.
4. [4]The Korea Herald, 'Korea starts using int'l age system, but exceptions remain' (2023). Secondary source for the concrete scope of the surviving exceptions: alcohol and tobacco from 1 January of the year a person turns 19, conscription examinations by birth year, elementary-school entry from 1 March of the year after a child turns 6 in international age, and lower-grade public-service examination eligibility by birth year. Retrieved 2026-07-30.
5. [5]International Organization for Standardization, ISO 8601-1:2019 — Date and time: representations for information interchange, Part 1: Basic rules. The YYYY-MM-DD calendar-date form both inputs on this page use. The full text is a purchased standard and was not opened; only the calendar-date representation is relied on, and it is uncontroversial.