How is a HETU structured?

It is the date of birth as DDMMYY, a century sign (+ for the 1800s; -, Y, X, W, V or U for the 1900s; A–F for the 2000s), a three-digit individual number, and a control character. An odd individual number means male, an even one means female.

How is the control character verified?

The nine digits DDMMYYZZZ are read as an integer and taken modulo 31. The remainder indexes into the string 0123456789ABCDEFHJKLMNPRSTUVWXY to give the expected control character. This tool implements that exact algorithm and compares the result.

Is my HETU sent anywhere?

No. Decoding is entirely client-side. The HETU never leaves your browser and there are no network requests. The tool does not query the population register.

Finland HETU Decoder (Henkilötunnus)

Finland HETU decoder

Enter a Finnish HETU (henkilötunnus) and the tool decodes the date of birth, the individual number and the gender, then verifies the control character.

It resolves the century from the sign character (+ for the 1800s; -, Y, X, W, V, U for the 1900s; A–F for the 2000s), reads sex from the individual number (odd = male, even = female), and recomputes the control character as the modulo-31 remainder of the nine digits DDMMYYZZZ mapped through 0123456789ABCDEFHJKLMNPRSTUVWXY.

Privacy-first: your HETU is processed entirely in your browser — nothing is uploaded or sent anywhere. The tool does not query the Finnish population register.