Address Verification

ZIP Code Lookup

By 31 March 2024April 28th, 2024No Comments
zip code api lookup

ZIP Code Lookup: What Is It and How to Benefit From It?

Businesses need USPS ZIP code lookup for many reasons, including creating accurate mailing lists and making decisions.

ZIP codes help understand customers’ locations, letting companies know their most customer-dense areas and how to expand sales.

But that is not all!

what is zip code

ZIP codes have many use cases, which makes using ZIP code lookup a must. This blog discusses the meaning and uses of ZIP codes—with how to use the ZIP code lookup on the USPS website.

What Are ZIP Codes and How Do They Work?

A ZIP Code is a 5-digit numerical code that designates a specific destination post office or mail delivery area, determining the final sorting and delivery location for letters. It signifies a grouping of delivery routes utilized by mail carriers and regions serviced by the United States Postal Service (USPS).

The acronym “ZIP” in ZIP Code stands for “Zone Improvement Plan.” The 5-digit ZIP Code consists of three primary components: the national area, the region or city, and the delivery area.

USPS has divided the United States into ten ZIP Code areas, numbered 0-9, starting in the northeast. You can use the ZIP code lookup USPS to find them for specific locations.

Understanding a ZIP Code

Before diving deep into what is USPS ZIP code lookup, please consider the following ZIP Code example: 91001. Once the first number is assigned based on the National Area, the subsequent two numbers are allocated according to a city, often starting with the main town or city in that region. The ZIP Codes then progress alphabetically.

The initial three digits of a ZIP Code collectively indicate the central mail processing facility, also known as a sec center or sectional center facility, to which the ZIP Code belongs. This facility serves as a specific zone or area's mail sorting and distribution center. 

Some sectional center facilities may have multiple three-digit codes assigned, making ZIP code lookup complicated. For instance, Merrifield's Northern Virginia sectional center facility has the ZIP Codes starting with 220, 221, 222, and 223.

The fourth and fifth digits of the ZIP Code signify the specific area within the city or town. For instance, if a letter carries the ZIP Code 47722, the USPS can deduce that it is in Indiana (4), Vanderburgh County (77), and the vicinity of the University of Evansville (22).

Matching ZIP Codes With Different Places

Only some US locations have a ZIP code. Thus, using USPS ZIP code lookup only works sometimes. 

There are insufficient deliverable addresses to establish a mail route, rendering a ZIP code unnecessary—primarily in remote and rural areas. If you're seeking seclusion or to live off the grid, these regions represent some of the most isolated areas in the country.

Assigning ZIP codes to specific counties adds another layer of complexity, with as much as 25% crossing county lines. The same complexity arises when associating ZIP codes with congressional districts, metro areas, time zones, area codes, and more, often leading to overlapping boundaries. 

Thus, businesses should be careful when using USPS ZIP code lookup by address for mailing, marketing, and other purposes.

It's crucial to understand that ZIP codes help streamline mail delivery. They might not necessarily align with established boundaries like cities, counties, or states.

If it is more practical for a mail carrier to cross state lines to deliver mail, the ZIP code “boundary” may extend beyond state lines, although this is not the norm. Some ZIP codes, such as 65733, 71749, and 73949, serve as examples of codes that cross state lines.

City assignments further complicate matters for USPS ZIP code lookup by street address, as the USPS only sometimes uses the actual city where a ZIP code is situated. The assignment of cities to ZIP codes is more general, usually reflecting the name of the main post office.

For example, many ZIP codes in St. Louis County, Missouri, are labeled as Saint Louis, even though they may more accurately correspond to the names of smaller cities within the county.

:bulb: Also Read: Zip Code Validation

Where Does the ZIP Go in the USPS Address Format?

The U.S. Postal Service employs a standardized format for all U.S. addresses, emphasizing using uppercase letters to prevent confusion. Ensure you include the apartment or suite numbers where applicable, employing valid USPS acronyms and abbreviations without periods. 

Here is an example of where to add ZIP codes to make USPS ZIP code lookup easier for your company:

Miller Inc.
8 5th AVE
New York City NY  10110-0001

Like the example above, senders must use a single space between city and state and a double space between state and ZIP code for optimal accuracy and delivery speed. Additionally, employ a nine-digit ZIP code.

While many individuals may be unaware of the four-digit code associated with their ZIP codes, prompting a potential challenge in obtaining such information from clients, leads, or customers, a USPS ZIP code lookup tool can seamlessly append these codes.

Beyond adhering to the fundamental USPS standard format, there are essential considerations for effective mail processing:

  1. Place the suite or apartment number above the delivery address if space is insufficient on the same line instead of below it.
  2. Utilize a USPS address verification tool to determine the ZIP+4 code.
  3. When delivering mail to an address rather than a specific individual, address it to a generic title such as “Postal Customer,” “Occupant,” or “Resident” instead of a name.
  4. Pay careful attention to directionals like “east” and “west,” as their omission or inaccuracy may impede accurate mail delivery.
  5. Recognize that despite incorrect addressing, USPS might deliver some items after making some changes to the location. However, such errors incur additional costs and resources for the Post Office, leading to surcharges for your business.

Using the USPS ZIP Code Lookup

You can search ZIP codes on the USPS website by entering the street address, city, or state.

However, the USPS ZIP code lookup by address or other elements does not confirm whether a person or organization is at the location.

Also, try searching for company locations with and without the organization’s names if you don’t get proper results with one search. You can also use different versions of these names until you find the correct ZIP code.

Input whatever address details you have, whether comprehensive or minimal. With a complete address, you can ascertain the deliverability of mail to that specific location.

If you only input a street name with the city and state or ZIP code, you get a compilation of all house numbers on that street. 

Alternatively, entering a house number and ZIP code yields a roster of all addresses sharing that house number within that ZIP code.

However, this tactic might be daunting and time-consuming to conduct a ZIP code lookup or search.

Hence, you can use PostGrid’s address verification API to add missing ZIP codes to your mailing lists.

PostGrid can

  • Add missing address data.
  • Check whether your existing ZIP codes are correct.
  • Add ZIP+4 codes to make your addresses more deliverable.
  • Provide geocoding, DPV, and other additional information.
  • Standardize, parse, and validate all postal addresses within the US and outside.
  • Help you get the benefits of USPS ZIP code API lookup without doing anything in-house.

Request a demo now to understand how ZIP code lookup works and how we help!

Ready to Get Started?

Start transforming and automating your offline communications with PostGrid


Explore Address Verification

Understanding USPS API and Address Validation Web Service