The fact that we have zip codes is nothing new. However, what is a 9 digit zip code? That is a question not everybody seems to be able to answer. We are used to zip codes having only five numbers after all, and this addition of four extra digits is confusing to many. Hopefully, the following information will help clarify some of the most pertinent questions you may have on the matter.

What Is a 9 Digit Zip Code?

A 9 digit zip code has an extra four numbers added to the end of it. It is also referred to as the “four digit extension”, the “full zip code”, and the “zip +4 code”. All mean the same thing. Interestingly, the U.S. Postal Service uses the latter way of calling it, which is the “zip +4 code”.

Finding Zip Code By Address:

If you want to know what the zip +4 code is, you have to have someone’s address. The last four digits included in it do not refer to the city, but they refer to either a Post Office box or a street address within a location. That location, in turn, is indicated by the first five digits of the zip code.

What the First Five Digits Mean:

A zip code’s first five digits tell you where in the country an address is, and which delivery office should receive the mail. The first zip codes, which all start with a 0, are in the northeast of the country. As you move southwest, that first number becomes gradually higher. The furthest, such as Beverly Hills, CA, starts with a 9.

Meaning of Digits Six and Seven:

Digits six and seven, the first two of the +4 numbers, in other words, point to a delivery sector. This could be a small geographical area, a large apartment building, a single high rise building, several office buildings, a group of Post Office Boxes, a group of streets, or several blocks. The other two digits, meanwhile, show a delivery segment. This could be a specific Post Office Box, a specific apartment within an office block, a certain side of the street, or a specific floor in a larger building.

So what is a 9 digit zip code? It is essentially a way for you, as a sender, or the postal worker, who delivers the mail, to know exactly where a piece of mail should be taken to. It is good to know these codes, and particularly your own, not in the least because it is now a requirement on many official pieces of documentation. That being said, the U.S. Postal Service has not yet mandated that the +4 code has to be added to all letters and packages. Rather, if you do include it, your mail won’t have to get handled as often, and there is less chance of something being delivered in error or to the wrong place. Lots of databases now exist where you can look up a zip +4 code, so if you are not sure of where to send something to, you can always look it up.