Quick answer
Korean age is birth year subtracted from the current year, plus one. Since June 2023 South Korea uses international age for almost all official purposes, so always label which system a number came from.
How the count actually works
International age asks a question about elapsed time: how many complete years have passed since the birth date. Korean age asks a different question entirely — which calendar year is this, and which calendar year were you born in? A baby is counted as one year old at birth, and everyone gains a year together on 1 January rather than on their own birthday.
That produces a simple formula: current year minus birth year, plus one. Someone born in November 1994 is 33 in Korean age throughout 2026, while their international age is 31 until their November birthday and 32 afterwards. The gap is two years for most of the year and one year after the birthday passes — which is exactly why the two numbers so often disagree by a value people cannot explain.
Use this guide with the right tool: Open the Korean Age Calculator for Korean age reckoning alongside international age for the same birth date. If the question shifts, compare it with the East Asian Age Calculator or the Age Calculator.
What changed in 2023
In June 2023 South Korea standardised on international age for legal and administrative matters. Contracts, medical records, official forms and most public documents now use completed-years age. This was not a ban on traditional counting; it was a decision about which number governs when a rule depends on age.
A separate system still applies in a few contexts, most visibly conscription and some age-restricted regulations, which use the year-difference count without the plus one. So there are effectively three numbers in circulation. When a form asks for age, the safe move is to give international age unless the form says otherwise, and to write the date of birth alongside it.
When the distinction matters
The distinction matters most where a threshold sits nearby. Eligibility for a school year, an insurance band, a benefit or an age-restricted purchase is decided by whichever system the rule names — and a two-year discrepancy is more than enough to move someone across a boundary.
It also matters in translated records. A birth year copied from a Korean-language document into an English form can silently carry the traditional count with it. If you are reconciling two records that disagree, check whether the difference is exactly one or two years and whether the birthday has already passed this year; that pattern usually identifies the cause immediately.
Recording it without ambiguity
The cleanest record is the date of birth itself, because every system can be derived from it. Where you must record an age, write the system next to the number: "32 (international)" removes the ambiguity in four characters.
For genealogy, medical history and immigration paperwork, keep the original document's figure and add your converted figure as a separate line rather than overwriting it. A reviewer can then see both and check your arithmetic instead of having to guess which convention the file was built on.
Worked example
The shape of the calculation stays the same with your own figures. What changes is the source of the rule, so check that before treating the number as settled.
Common mistakes to avoid
- Assuming the gap is always one year. For most of the calendar year the gap is two, because the birthday has not yet occurred. It narrows to one only after the birthday passes.
- Converting an age instead of a birth date. Converting an age alone loses information. Go back to the date of birth and recalculate; otherwise a rounding error becomes permanent.
- Treating the 2023 change as retroactive to old records. Documents produced before the change may still carry traditional counts. Date the record, then interpret the number in the convention that applied when it was written.
Use the right calculator
Start with whichever matches the information you already hold. The other two are there for when the question shifts.
Frequently asked questions
Is Korean age still used in daily life?
Yes. The legal standard changed, but traditional counting remains common in conversation, in describing school cohorts and in some cultural contexts. It simply no longer decides official questions.
Does everyone really age on 1 January?
Under the traditional count, yes — the number changes for everyone at the turn of the calendar year rather than on individual birthdays.
Which number should I put on a form?
International age, unless the form explicitly asks for something else. Where there is space, include the date of birth so the reader can verify it.