How is the century determined?

The century comes from the individual number (digits 7-9) combined with the two-digit year — for example, individual numbers 500-999 with a year of 00-39 indicate a birth in 2000-2039.

How accurate is the checksum verification?

The decoder recomputes both official modulus-11 control digits from the weight vectors and compares them to the number, so a structurally valid number with a correct checksum is internally consistent — but a valid checksum does not prove the number was actually issued to a real person.

How is gender encoded in a fødselsnummer?

Gender comes from the ninth digit — the last digit of the individual number. An odd digit means male (Mann); an even digit means female (Kvinne).

A D-number is a temporary identity number assigned to people with a short-term relationship to Norway, such as foreign workers. It is recognised because 40 is added to the day of birth, so the first digit is 4-7 instead of 0-3.

An H-number (help number) is a temporary internal number used by some systems when a real fødselsnummer is unavailable. It is recognised because 40 is added to the month, so the third digit pattern is shifted.

Is my fødselsnummer sent anywhere?

No. The decoder is privacy-first — all processing happens locally in your browser and the number never leaves your device.

Norway Fødselsnummer Decoder

The Norwegian fødselsnummer is the 11-digit national identity number assigned to residents of Norway. This decoder reads the information packed into it — date of birth, gender, individual number and the two checksum digits — entirely in your browser.

How it works

The 11 digits split into three parts: DDMMYY (date of birth), a three-digit individual number, and two control digits.

Date of birth comes from the first six digits, with the century derived from the individual number combined with the two-digit year.
Gender is read from the last digit of the individual number: odd = male, even = female.
The two modulus-11 control digits are recomputed using the official weight vectors 3 7 6 1 8 9 4 5 2 (K1) and 5 4 3 2 7 6 5 4 3 2 (K2) and compared to the supplied digits.
A D-number is detected when 40 is added to the day, and an H-number when 40 is added to the month.

Example

For an ordinary number whose date portion reads 150693 with individual number 456:

Part	Value	Meaning
Day-Month-Year	15-06-93	15 June 1993
Individual	456	last digit 6 → even → female
Control digits	recomputed	compared for consistency

If the day portion were 55 (15 + 40) instead, the decoder would flag it as a D-number.

It is privacy-first: nothing leaves your browser. The decoder only interprets the structure and checksum of the number — it does not check it against any register.