The Geolocating Number Patterns Hidden Within Most Zip Codes and Post Codes Around the World

CGP Grey explains, in his rather forthright manner, how zip codes are assigned in the United States and post codes around the world, noting how each number is essentially a pattern of numbers that geolocates where a posted letter should go.

For every letter to get where it’s going requires the address obviously but also a mysterious string of characters called a post code but if there’s an address already what’s the point of the postcode exactly isn’t this just like the address again kind of yes but also no? 

There are of course exceptions to these rules.

There are sorting centers scattered strategically. Each numbered and each sorts the mail for the post offices it can reach efficiently so if you live on the edge of your state but near another state’s sorting center your zip code follows the sorting code not the state line.

And, as with most things, other countries seem to have a better system, particularly Ireland.

There’s no order to maintain at all if your mailbox never moves or your code never changes. That’s the method to the madness. So when Ireland…found a new answer, make a post code so precise it becomes the perfect address. So while everywhere else, you have to write both the destination, in Ireland you can write both, probably still should write both, but you don’t have to because just the post code alone will do.