Quick answer: International age counts the full years since you were born, starting at 0. Korean age (the traditional “counting age”) starts at 1 at birth and adds a year every January 1. To get it, take the current year, subtract your birth year and add 1. That means Korean age is one or two years higher than international age.
Example: someone born on 31 December 2000 is 25 by international age on 10 October 2026, 26 by “year age”, and 27 by Korean counting age.
To check your own international age, use our free age calculator. To understand the math behind it, read how to calculate your age by hand.
Key takeaways
- International age = full years since birth (the standard in most of the world).
- Year age = current year − birth year.
- Korean counting age = current year − birth year + 1.
- South Korea moved official and legal use to international age in June 2023, with a few exceptions.
- Insurance age is a separate idea. It’s based on your nearest birthday, so it can be a year higher than your actual age.
Why Are There Different Ways to Count Age?
Age sounds simple, but it depends on what you count and when you start. Some systems count the years that have passed. Others count calendar years you’ve lived in. Insurers use their own rule, because age affects the price of cover.
So one person can have several “correct” ages on the same day. The skill is knowing which one a form, law or conversation wants.
The Four Age Systems at a Glance
| System | Starts at | Goes up on | Formula |
|---|---|---|---|
| International age | 0 | Your birthday | Full years since birth |
| Year age (calendar age) | 0 | January 1 | Current year − birth year |
| Korean counting age | 1 | January 1 | Current year − birth year + 1 |
| Insurance age (age nearest birthday) | Varies | At the 6-month point before your birthday | Rounds to your nearest birthday |
International Age: The Standard Method
International age is what most countries use. It’s the number of years since you were born, and it starts at zero. You turn one on your first birthday, and you gain a year on each birthday after that.
How to calculate it
- Subtract your birth year from the current year.
- If your birthday hasn’t happened yet this year, subtract 1.
Example: born 14 March 2000, date 10 October 2026
- 2026 − 2000 = 26
- Birthday has passed → 26
For exact years, months and days, follow the full method in our guide to calculating your age by hand, including leap years and Feb 29.
Korean Age (Counting Age): How It Works
In the traditional Korean system, a person is considered one year old at birth. They then gain a year every January 1.
That produces two quirks:
- A baby born on 31 December is 1 on the day of birth and 2 the next day, on January 1.
- Everyone born in the same calendar year has the same Korean age, whatever their birthday.
How to calculate it
Korean age = current year − birth year + 1
Example: born 14 March 2000, in 2026
- 2026 − 2000 + 1 = 27
At the same time, that person’s international age is 26. The Korean age is one year higher because of the “+1”.
Year Age (Calendar Age): The Middle System
The “calendar age” is a hybrid of the other two: babies are zero on the day they’re born, and a year is added every January 1.
Formula: current year − birth year
Example: born 14 March 2000, in 2026 → 2026 − 2000 = 26
Year age matches international age after your birthday has passed, and runs one year ahead of it before your birthday.
How Different Can the Ages Be? (A Worked Table)
Here are ages on 10 October 2026 for people born in 2000, with different birthdays:
| Date of birth | International age | Year age | Korean age |
|---|---|---|---|
| 1 January 2000 | 26 | 26 | 27 |
| 14 March 2000 | 26 | 26 | 27 |
| 10 October 2000 | 26 | 26 | 27 |
| 11 October 2000 | 25 | 26 | 27 |
| 20 November 2000 | 25 | 26 | 27 |
| 31 December 2000 | 25 | 26 | 27 |
What the table shows:
- Korean age is the same for the whole birth year (27).
- International age changes at the birthday (26 before, 25 after).
- Korean age is 1 or 2 years higher than international age. Most South Koreans’ “Korean age” could be one or even two years older than their international age. krdo
- For anyone born in the second half of the year, the gap is two years until their birthday.
What Changed in South Korea in 2023?
South Korea implemented a law on 28 June 2023 that standardized age counting to the international norm. The revised law requires international age across all judicial and administrative areas. This means official documents, contracts and public services use international age.
What stayed the same?
A few rules kept the older “year age” method. The legal age for buying alcohol and tobacco stays calculated the old way, so people can buy from 1 January of the year they turn 19 by international age. Eligibility for national military service also keeps the traditional formula. School entry age and the age for public servant examinations are also unaffected. Korea starts using int'l age system, but exceptions remain +2
Officials said the exceptions help keep schools, the military and age-restricted products consistent with how age groups have always been grouped. Reports suggest lawmakers have discussed reducing the exceptions, so check current rules for any legal question. This article is not legal advice.
In daily life
Many people in Korea still use Korean age casually, especially when asking someone’s age socially. But for official purposes, international age is the norm.
What Is Insurance Age?
Insurance age is a different idea. It isn’t about culture. It’s a pricing rule used by many life insurers, and it may not match your actual age.
Insurers commonly use one of two methods:
- Age last birthday: your actual age in completed years.
- Age nearest birthday: the age you’re closest to. If it has been six months or more since your last birthday, your insurance age is the age you’ll turn at your next birthday.
Example: A person aged 28 years and 7 months has a life insurance age of 29, while someone aged 28 years and 4 months has a life insurance age of 28.
Worked examples on 10 October 2026:
| Date of birth | Actual age | Time since last birthday | Insurance age (nearest) |
|---|---|---|---|
| 14 March 1996 | 30 | 6 months 26 days | 31 |
| 14 July 1996 | 30 | 2 months 26 days | 30 |
| 31 December 2000 | 25 | 9 months 10 days | 26 |
Insurance age can be one year higher than your international age, which can raise the premium. Many insurers allow the policy date to be back-dated by up to six months to keep a lower age. Rules differ by company and country, so ask your insurer or an advisor which method applies to you. This is general information, not financial advice.
Other East Asian Age Systems
Korea isn’t the only place with traditional age counting. Several East Asian cultures have historically used a “nominal age” that starts at 1 or changes at the new year, rather than on the birthday. Many have moved to international age for official use. If you work with documents from a specific country, check which method the form expects.
Which Age Should You Use?
| Situation | Age to use |
|---|---|
| Passports, official forms, medical records | International age |
| Most contracts and public services in South Korea | International age (since 2023) |
| Alcohol and tobacco purchase in South Korea | Year age rule (from 1 January of the year you turn 19) |
| South Korean military service eligibility | Year age rule |
| Life insurance quote | Insurer’s rule (often age nearest birthday) |
| Casual conversation in Korea | Often Korean counting age |
| Health charts for children | Exact age in years and months (see BMI by Age and Sex) |
When in doubt, use international age and say so.
Common Mistakes with Age Systems
- Assuming one age fits every form. Always check what is asked.
- Forgetting the “+1” when converting to Korean age.
- Using Korean age for official forms. It’s no longer standard in Korea either.
- Mixing year age and international age. They differ for anyone whose birthday hasn’t happened yet.
- Assuming insurance age equals actual age. It may be a year higher.
- Ignoring leap day birthdays. Feb 29 births have their own conventions, covered in our age calculation guide.
Korean Age vs International Age: FAQs
What is the difference between Korean age and international age?
International age counts full years since birth, starting at 0. Korean age starts at 1 and adds a year every January 1.
How do I convert international age to Korean age?
Take the current year minus your birth year, then add 1.
How do I convert Korean age to international age?
Subtract 1 or 2. Subtract 1 if your birthday has passed this year, and 2 if it hasn’t.
Is Korean age still used?
Socially, yes. Officially, no: South Korea adopted international age for legal and administrative use in June 2023, with a few exceptions.
Why is Korean age one or two years older?
Because it starts at 1 at birth and increases every January 1 for everyone.
What is year age (calendar age)?
It’s your current year minus your birth year. It starts at 0 and goes up on January 1.
What is insurance age?
A pricing age used by many insurers. It’s often your age nearest birthday, so it may be a year higher than your actual age.
What age should I put on a form?
Usually international age, unless the form specifies another method.
Does the age system affect my age in days?
No. Your real time alive is the same under every system. Only the label changes.
Calculate Your International Age in Seconds
Use our free age calculator to calculate your international age in years, months and days. Then apply the Korean age or year age formula if you need it. For other tools, explore our unit conversion tools or visit ConversionFree.
