Home postinumero Finland
Finland Postinumero validator
How the postinumero format works
- Format
- 5 digits
- Example
- 00100
Things to watch for
- Format-only check — does not confirm the postinumero actually exists
- Always exactly 5 digits with no separators
- The leading '00' block is reserved for Helsinki; other regions start higher
^[0-9]{5}$A Finnish postinumero is the 5-digit postcode Posti uses to route mail, written directly before the city name — for example 00100 Helsinki. The system dates to 1971, and Helsinki was given the entire leading 00xxx block, so any address starting with two zeros is somewhere in the capital. Anyone validating a Finnish shipping address, a checkout form, or a spreadsheet of Finnish customer records needs the postinumero in the correct 5-digit shape before it’s trusted.
Because it’s a bare run of digits with no letters or separators to anchor against, a dropped or duplicated digit produces a code that’s still superficially plausible — the kind of error that’s cheap to catch at entry and expensive once a parcel has already been sorted to the wrong district.
How this validator works
This tool checks that the input is exactly 5 digits with no letters, spaces, or hyphens, entirely in your browser, with nothing sent to a server.
What a pass doesn’t tell you
A postinumero carries no check digit, so matching the 5-digit shape is the most a client-side tool can confirm — not that Posti has assigned it to a real district. Confirming that requires Posti’s own postcode search.
Scope: this page and tool cover format validation only — not address lookup or confirming a postinumero is currently in use.
postinumero FAQ
What is a postinumero and how many digits does it have?
Postinumero is Finnish for 'postal number' — the country's 5-digit postcode, introduced in 1971. It's written as a plain 5-digit run directly before the city name, e.g. 00100 Helsinki.
Why do so many Helsinki postcodes start with 00?
Posti reserved the entire 00xxx block for Helsinki when the system launched, a deliberate choice that put the capital first in the national numbering scheme. The rest of the country's postal districts start from 01xxx upward.
Does a correctly formatted postinumero mean it actually exists?
No. This tool only confirms the string is 5 digits — it doesn't check it against Posti's actual assignment list. Confirming a postinumero is real, and seeing which district it names, requires Posti's own postcode search.