Korean RRN Decoder
Decode a 13-digit Korean Resident Registration Number for birthday, age, gender, and zodiac. Standards-compliant checksum check catches typos. Input never leaves your browser.
How to Use
Type the 13-digit number. A hyphen is inserted automatically after the 7th digit (e.g., 900101-1234567).
Birthday, gender (M/F), nationality (Korean / foreigner), age, Korean age, zodiac animal, and Western zodiac sign appear instantly.
The last digit is verified by the official algorithm (weighted sum mod 11). Invalid or fabricated numbers show a red ✗.
FAQ
Is the RRN sent to a server?
No. All decoding runs in your browser via JavaScript — no network calls, no localStorage or cookies. The value is wiped when you close the tab. You can verify in the Network panel.
How is the checksum computed?
Multiply the first 12 digits by weights [2,3,4,5,6,7,8,9,2,3,4,5], sum them, then "(11 − sum mod 11) mod 10" must equal the 13th digit. This is the official Korean government formula.
Is the zodiac animal based on the Gregorian year?
This tool uses the Gregorian birth year from the RRN. Korean tradition rotates the zodiac on lunar New Year (1st of the 1st lunar month), so Jan–Feb births may technically belong to the previous year's animal. Use the "Lunar Calendar" tool for precise lookup.
Difference between Western age and "Korean age"?
Western age (now the official standard in Korea since 2023): years since birthday. Korean age: current year − birth year + 1, everyone ages on New Year's Day. A baby born Jan 1, 2024 is age 0 (Western) but 1 (Korean) on Jan 1.
Where is the data stored?
Nowhere. Reloading or closing the tab wipes the input from memory. Nothing is written to localStorage, cookies, or any server.
