What Is Lunar Age?
Lunar age — also called East Asian age reckoning or "nominal age" — is a traditional way of counting a person's age used in China, Korea, Vietnam and historically in Japan. Unlike the Western system, a baby is considered 1 year old at birth, and everyone gains a year together at the lunar new year rather than on their individual birthday. This means a person's lunar age is usually one or two years higher than their international age.
How to Use the Calculator
Enter your birth year and the current year. The calculator returns your lunar (nominal) age along with an approximate Western age for comparison. Because lunar age is based on the calendar year of birth, you do not need to enter your exact birth date for this nominal calculation.
The Formula Explained
The core formula is simply $$\text{Lunar Age} = \text{Current Year} - \text{Birth Year} + 1$$ The "+1" reflects the convention that life is counted from conception/birth as year one. For example, someone born in any month of 2000, evaluated in 2024, is \(2024 - 2000 + 1 = 25\) in lunar age, while their Western age is 23 or 24 depending on whether their birthday has passed.
Worked Example
Birth year 1990, current year 2024: Lunar age = $$2024 - 1990 + 1 = \mathbf{35}$$ Approximate Western age = \(2024 - 1990 = 34\).
FAQ
Why is my lunar age higher? Because counting starts at 1 at birth and everyone ages at new year, so the gap is typically 1–2 years.
Does Korea still use this? In 2023 South Korea standardized official documents to international age, but lunar/Korean age is still common in daily conversation.
Do I need my exact birthday? No — nominal lunar age depends only on the birth year and current year.
