Find the full ZIP+4 for any US address
The five-digit ZIP gets mail to a post office. The four extra digits get it to a specific block, building, or box. Enter an address below — it is free and needs no account.
What the last four digits actually mean
A ZIP+4 segment is not a smaller area in the way people expect. It is a point on a letter carrier's route, and in practice one segment means:
- One side of one block — the odd numbers between two cross streets
- A single large building, or one floor of it
- A group of PO boxes, sometimes a single box
- A single business receiving enough mail to warrant its own code
That is why there is no ZIP+4 for a town, or even for a street. Two neighbours facing each other across the same road usually have different last-four digits, because they sit on opposite halves of the carrier's walk. It is also why a lookup needs a full street address rather than a city: the four digits are a property of the delivery point, not the place.
What you get back
The nine digits are the headline, but the rest of the result is usually what stops a problem before it costs money:
| Standardized address | The address as USPS writes it — correct suffix, correct directional, correct unit designator. Use this wording everywhere rather than your own. |
|---|---|
| Delivery point confirmation | Whether USPS confirms mail can actually be delivered there. A result confirming the building but not the unit means your unit number is wrong or missing — the most common cause of intermittent delivery failures in apartment buildings. |
| Residential or business | Private carriers price these differently, so getting it wrong costs a surcharge on every parcel. |
| Vacancy flag | Whether USPS has recorded the address as unoccupied for 90 days or more. Pure waste on a mailing list. |
| County, carrier route, coordinates | County with its FIPS code, the carrier route serving the address, time zone, and a geocode. |
When a lookup comes back empty
Almost always one of five things, roughly in order of frequency:
- The ZIP does not match the street. The single most common cause. Try dropping the ZIP and giving the city and state instead — we will find the right one.
- A missing unit number in a building that requires one.
- The address is genuinely new. New construction takes time to appear in USPS files.
- It is not a delivery point at all — a vacant lot, a building entrance without mail service, a business inside another business.
- A typo in the street number, which is easy to miss because everything else looks right.
Who uses this
- People sending something important — a passport application, a legal filing, a package that has already gone missing once.
- Anyone running a mailing. Accurate ZIP+4 data is what qualifies a mailing for presort discounts, and vacancy and deliverability flags cut the pieces that would have been wasted.
- Online stores. Validating an address at checkout catches the typo while the customer is still on the page, which is far cheaper than a returned parcel and a support ticket.
- Developers who need address validation, tax jurisdiction, or delivery-point data behind a REST API.
Doing this more than once
Upload a spreadsheet and get every row appended with ZIP+4, county, carrier route, and delivery-point data — or call the API from your own application. Repeat lookups of the same address are served from cache and never counted against your allowance.
Browse ZIP codes
Every US ZIP code has its own page with county, time zone, area codes, and nearby codes. Browse all of them by state.
Common questions
What is a ZIP+4 code?
A ZIP+4 is the nine-digit form of a US postal code: the familiar five digits, a hyphen, and four more. The five digits get mail to a post office. The four extra digits identify a delivery segment inside it — usually one side of one block, a single building, or a run of PO boxes.
How do I find the ZIP+4 for my address?
Enter the street address in the box at the top of this page. You need the street number and either the ZIP code or the city and state. If the address is in an apartment building, include the unit number — without it we can confirm the building but not the specific delivery point.
Is the ZIP+4 required?
Not for ordinary mail. A five-digit ZIP is enough to get a letter delivered. ZIP+4 matters commercially: most USPS bulk and presort postage discounts are priced on accurate ZIP+4 data, and address-verification systems use it to confirm a delivery point actually exists.
Why does my neighbour have a different ZIP+4?
Because a segment usually covers one side of one block. Houses facing each other across a street sit on different halves of the carrier's walk, so they generally get different last-four digits even though every other part of the address matches.
Does a ZIP+4 ever change?
Yes. USPS revises delivery segments as areas are built out, renumbered, or rerouted, and the underlying files update monthly. If you hold addresses for a long time, revalidate them periodically rather than treating a ZIP+4 as permanent.
Is this free?
Lookups on this page are free and need no account. A free account adds 250 API lookups a month and bulk CSV processing. Paid plans start at $19 for 10,000 lookups.