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ZIP Code Lookup
Type a 5-digit US ZIP code to see its city and state, or type a city name and two-letter state abbreviation, like Denver CO or Austin TX, to find every ZIP code that serves that city. Both searches return results instantly with no sign-up required.
This is a fully secure tool. We do not store, track, or sell any information you enter.
How to use this tool
This tool works in two directions. You can start with a ZIP code and find out which city and state it belongs to, or you can start with a city and state and get back every ZIP code assigned to that area. Both lookups are useful at different moments: verifying an address someone gave you, filling out a form, or checking whether the ZIP code on an envelope matches the destination city before you send it.
Results appear as soon as you press Search. For most searches you will get one clear result. For city-based searches in larger metropolitan areas, you may get a list of several ZIP codes, which is normal and expected, since large cities are divided into many postal delivery zones. Use the full street address to determine which specific ZIP code applies if you need to get more precise.
Looking up a city from a ZIP code
Type any 5-digit US ZIP code into the search box and press Search. The result will show you the primary city name and state that USPS has assigned to that ZIP code, along with any alternate city names the same ZIP code serves. This is useful when you have received a ZIP code on a form or address label and want to confirm it is correct before mailing.
Looking up ZIP codes for a city
Type the city name followed by the two-letter state abbreviation, for example Chicago IL or Portland OR, and press Search. The tool returns every ZIP code assigned to that city in the USPS database. If you are addressing a letter and need to verify the ZIP code, cross-reference the result with the street address the recipient gave you, since different streets within the same city are often served by different ZIP codes.
Why the ZIP code matters more than the city name
A USPS sorting machine reads the ZIP code first and treats it as the source of truth. If the city name and ZIP code disagree, the ZIP wins and the letter is routed to wherever that ZIP actually points, not wherever the city name says. A correct ZIP code with a slightly wrong city name almost always still arrives; a correct city name with the wrong ZIP code often does not.
This matters especially for addresses near city boundaries. The mailing city name assigned to a ZIP code by USPS may be a neighborhood, suburb, or township name rather than the name of the major city nearby. A ZIP code in what most people call Los Angeles might be officially assigned to Culver City or Van Nuys in the USPS database. If you write the name of the major city instead of the USPS-assigned city, the letter will likely still arrive, because the ZIP code overrides the city name in sorting, but it is cleaner and more professional to use the exact name on file.
When your city search returns more than one ZIP code
Most US cities are divided into multiple postal delivery zones, each with its own ZIP code. New York City has more than 170 active ZIP codes. Chicago has roughly 60. Even mid-sized cities like Denver and Phoenix have dozens. When you search for a city by name, this tool returns every ZIP code assigned to that city, which is accurate, but means you need one more piece of information to find the right one for a specific address.
The most reliable way to identify the correct ZIP code for a specific street address is to look it up by full address rather than by city. That level of lookup requires address-level data from the USPS, which this tool will support once the USPS API integration is complete. Until then, if you receive multiple results and need to confirm the correct ZIP, the safest approach is to ask the recipient directly or verify using the USPS ZIP Code Lookup tool at usps.com, which accepts full street addresses.
What is a ZIP code?
ZIP stands for Zone Improvement Plan. The five-digit postal code system was introduced by the United States Postal Service in 1963 to replace a manual sorting system that had become too slow for the volume of mail the country was generating. Before ZIP codes, mail was sorted by hand using city names and street knowledge. ZIP codes allowed automated sorting machines to handle the process instead, dramatically speeding up delivery times and reducing errors.
There are more than 41,000 active ZIP codes in the United States. They cover all 50 states, the District of Columbia, and US territories including Puerto Rico, Guam, the US Virgin Islands, American Samoa, and the Northern Mariana Islands. Some ZIP codes belong to a single building: the Pentagon has its own ZIP code (20301), as do several major corporations that receive extremely high mail volumes. Most ZIP codes, however, cover a neighborhood, a carrier route, or a cluster of delivery points served by a single post office.
How ZIP codes are structured
The five digits in a ZIP code are not arbitrary: each position carries a specific geographic meaning. The first digit identifies one of ten national areas, moving roughly from the Northeast to the West Coast: 0 covers Connecticut, Maine, Massachusetts, New Hampshire, New Jersey, New York, Puerto Rico, Rhode Island, and Vermont. 9 covers Alaska, California, Hawaii, Nevada, Oregon, and Washington. The second and third digits together identify a Sectional Center Facility (SCF), the regional mail processing hub that handles all mail for that area. Most mail passes through two or three SCFs before it reaches the local post office.
The fourth and fifth digits narrow delivery down to a specific post office or local carrier area within that region. This is the level where a letter transitions from regional sorting to the final mile of delivery. Understanding this structure helps explain why a wrong ZIP code is such a serious addressing error: a single wrong digit in the first position can route your letter to a processing facility hundreds of miles away from the intended destination, while a correct ZIP code with a misspelled city name will usually still arrive on time.
ZIP codes for special address types
Not every ZIP code follows standard delivery geography. Military addresses use special ZIP codes assigned to APO (Army Post Office), FPO (Fleet Post Office), and DPO (Diplomatic Post Office) addresses. These ZIP codes are formatted like standard 5-digit US ZIP codes and are treated as domestic mail by USPS, but they route through military mail distribution centers rather than the standard civilian postal network. Military ZIP codes will return a result in this tool, showing the APO, FPO, or DPO designation along with the relevant state abbreviation (AA, AE, or AP depending on the region).
PO Box addresses sometimes use a different ZIP code than the street delivery ZIP code for the same city. A post office may be assigned a ZIP code specifically for its PO Boxes, separate from the ZIP codes used for the surrounding neighborhood. If you are addressing an envelope to a PO Box and the recipient has given you their PO Box number, use the ZIP code they provided; do not substitute the street delivery ZIP for the same area. US territories including Puerto Rico (ZIP codes starting with 006 through 009), Guam (969), and the US Virgin Islands (008) are included in this tool's database.
ZIP+4: the nine-digit ZIP code
ZIP+4 is an extended version of the standard 5-digit ZIP code. The four additional digits, added after a hyphen, like 80202-1234, identify a specific city block, floor of a building, cluster of PO Boxes, or rural delivery segment within the 5-digit ZIP code zone. USPS introduced the ZIP+4 system in 1983 to allow mail to be sorted all the way to the delivery point mechanically, reducing the amount of hand sorting required by carriers. The result is faster processing and fewer errors for high-volume mailers.
You do not need a ZIP+4 code to send ordinary mail. A 5-digit ZIP code is sufficient for USPS to deliver a letter or package. ZIP+4 codes are most useful for businesses sending large volumes of mail, where the small improvement in sorting speed adds up across thousands of pieces. For individuals addressing a single envelope, the standard 5-digit code is all that is required. ZIP+4 lookup is coming to this tool once the USPS Address Information API integration is live: it will allow you to enter a full street address and receive the confirmed ZIP+4 for that specific delivery point.
What this tool covers
This tool supports 5-digit ZIP code lookup in both directions: enter a ZIP to get the city and state, or enter a city and state to get all associated ZIP codes. The database covers all active ZIP codes across the 50 US states, Washington DC, and US territories, and is updated to reflect the current USPS postal geography as of July 2026. It does not currently support full street address lookup, ZIP+4 lookup, or address deliverability validation. Those features require access to the USPS Address Information APIs and are in development.
The tool uses the GeoNames database, a widely used open geographic dataset licensed under Creative Commons Attribution. No query data is transmitted to an external server during your search. This is a fully secure tool: we do not store, track, or sell any information you enter.
Using your ZIP code to address an envelope
Now that you have the right ZIP code, use these guides to get the rest of the address right:
- How to address an envelope — the full format, line by line
- How to address an envelope with an apartment number — where the unit goes
- How to address an envelope to a PO Box — and which ZIP code to use
- How to address military mail — APO, FPO, and DPO addresses
- USPS envelope addressing standards — what Publication 28 says
Frequently asked questions
What does ZIP stand for?
ZIP stands for Zone Improvement Plan. The name reflects the original purpose of the system: to improve the efficiency of mail sorting and delivery by dividing the country into geographic zones that machines could process automatically.
The five-digit ZIP code was introduced by USPS in 1963. Before that, mail was sorted manually using city names and carrier knowledge, which became impractical as mail volume grew rapidly in the postwar era.
How many ZIP codes are there in the United States?
There are more than 41,000 active ZIP codes in the United States, covering all 50 states, the District of Columbia, and US territories. The exact count changes over time as USPS creates new ZIP codes for growing areas and retires codes for areas with declining mail volume.
A small number of ZIP codes are assigned to unique non-geographic entities: individual high-volume buildings, military installations, or government facilities, rather than to a standard geographic delivery area.
Can a city have more than one ZIP code?
Yes. Most cities of any significant size have multiple ZIP codes. Large cities have dozens or hundreds. New York City has more than 170. This tool returns all ZIP codes assigned to a city when you search by city name.
To find the right ZIP code for a specific address within a city, you need to search by the full street address rather than just the city name. That level of lookup is coming to this tool once the USPS API integration is live.
Can a ZIP code cover more than one city?
Yes. Some ZIP codes serve multiple small towns, communities, or neighborhoods within the same delivery area. When you look up such a ZIP code, the tool will show the primary city along with the alternate city names associated with it.
USPS designates one city name as the official preferred mailing name for each ZIP code. The alternate names are accepted, but the preferred name is what USPS has on file, and using it is more reliable when addressing formal mail.
Can a ZIP code cross state lines?
Rarely, but it does happen. A small number of ZIP codes in the United States cover delivery points in two different states because the routing was designed around carrier efficiency rather than political boundaries. ZIP codes 65733, 71749, and 73949 are well-known examples.
If you encounter a cross-state ZIP code, use the ZIP code provided by the recipient rather than trying to determine the "correct" one based on the state name alone.
Is a ZIP code the same as a postal code?
"Postal code" is the general international term for a country’s mail routing code system. "ZIP code" is the specific name used in the United States. Other countries use different names: Canada uses "postal code," the UK uses "postcode," and India uses "PIN code," but they all serve the same routing function.
When filling out international forms that ask for a "postal code," US residents should enter their 5-digit ZIP code. The field is asking for the same type of information under a different name.
What is ZIP+4 and do I need it when addressing an envelope?
ZIP+4 is a 9-digit code: the standard 5-digit ZIP followed by a hyphen and four additional digits. The extension identifies a specific block, floor, PO Box cluster, or delivery segment within the 5-digit zone. It allows mail to be sorted mechanically all the way to the delivery point.
You do not need ZIP+4 for everyday mail. A standard 5-digit ZIP code is sufficient for USPS to deliver your letter. ZIP+4 is mainly useful for high-volume business mailers, where the extra sorting precision reduces handling time at scale. See how to address an envelope for the full format guide.
Is the ZIP code or the city name more important on an envelope?
The ZIP code. USPS sorting machines read the ZIP code first and treat it as the authoritative routing instruction. If the city name and ZIP code disagree, the ZIP wins: the letter goes to wherever that ZIP code actually points, regardless of what the city name line says.
A correct ZIP code with a slightly misspelled city name will almost always still arrive. A correct city name with the wrong ZIP code often will not. See USPS envelope addressing standards for the full rule set.
Does this tool find ZIP codes for PO Boxes?
This tool returns ZIP codes by city name and state. PO Boxes sometimes use a different ZIP code than the street delivery ZIP for the same city: a post office may have a separate ZIP code assigned specifically to its PO Boxes.
If you need the ZIP code for a specific PO Box, the most reliable source is the recipient themselves, or the USPS ZIP Code Lookup tool at usps.com, which accepts PO Box numbers directly. Full address-level lookup, including PO Box support, is coming to this tool once the USPS API integration is complete.
Do ZIP codes ever change?
Yes. USPS periodically updates ZIP codes to reflect changes in population, mail volume, and delivery infrastructure. New ZIP codes are created for growing areas. Existing codes are sometimes split when a delivery area becomes too large for one carrier route, or consolidated when volume drops.
The database this tool uses is updated to reflect current USPS postal geography as of July 2026. If you are using ZIP code data for a business application, it is worth verifying against the USPS data source periodically to catch any changes.
What ZIP codes do US military addresses use?
Military addresses use ZIP codes assigned to APO (Army Post Office), FPO (Fleet Post Office), and DPO (Diplomatic Post Office) address types. These are formatted like standard 5-digit US ZIP codes and are treated as domestic mail by USPS, but they route through military mail distribution centers rather than standard civilian postal facilities.
The state abbreviation on a military address is not a US state, it is a region code: AA (Armed Forces Americas), AE (Armed Forces Europe, Middle East, Africa, and Canada), or AP (Armed Forces Pacific). These codes are searchable in this tool. See how to address military mail (APO/FPO/DPO).
My ZIP code search returned no results. What should I check?
A few common reasons: the ZIP code may not exist or may not be in active use; you may have typed a 4-digit or 6-digit number by mistake (US ZIP codes are always exactly 5 digits); or the ZIP code may belong to a special-use category not included in the current database.
If the ZIP code was provided by a recipient, double-check with them directly. If you are unsure whether a ZIP code is valid, the USPS ZIP Code Lookup tool at usps.com is the authoritative source for confirming active ZIP codes.
ZIP code data from GeoNames, used under a Creative Commons Attribution license. Data current as of July 2026.