US Address Format Rules: A Complete Guide

A US address is four short lines of text built on conventions the postal system has enforced for decades. Which word ends a street name, which two letters stand for a state, what the first digit of a ZIP says about geography — none of it is arbitrary, and knowing the rules explains most failures that look mysterious. This guide covers the format itself, so it works as a reference for filling in a form, validating a record, or building test data.

1. The layers of a standard address

A domestic address narrows from the recipient down to a single delivery point, in a fixed order:

• Recipient name — a person or a company, on its own line.
• Street line — house number, street name, street suffix, plus an apartment or unit designator when needed.
• City — the delivery city, which is not always the same as the municipal name people use locally.
• State — the official USPS two-letter abbreviation.
• ZIP — five digits, or five plus a four-digit extension.

City, state and ZIP share one line, separated by a comma or spaces: San Jose, CA 95113. A country line (USA) is added only for international mail; domestic mail omits it entirely.

2. The street line: number, name, suffix

The street line is where most mistakes happen, because it glues three components together in an order that cannot be rearranged: house number, street name, street type suffix. The suffix is not decoration — it is part of the name. Main Street and Main Avenue can be two different roads in the same city.

The common suffixes:

• St (Street) — the most common type.
• Ave (Avenue) — often wider than a street.
• Blvd (Boulevard) — a multi-lane arterial.
• Rd (Road) — a connector road in suburban or rural areas.
• Dr (Drive), Ln (Lane), Ct (Court) — common in subdivisions.
• Pl (Place), Way, Pkwy (Parkway) — equally valid, and equally wrong to drop.

House numbers are usually plain digits, with two exceptions that bring in a hyphen. A parcel covering a primary and secondary number may be written as a range like 1200-1298, and some older urban numbering uses fractions such as 12 1/2.

Directional prefixes — N, S, E, W — belong to the street name and sit in front of it, since they distinguish segments of the same name. 316 W Main St and 316 E Main St are far apart. Drop the letter and the match lands on the wrong side of town.

3. Apartments, suites and units

Multi-unit buildings need a designator appended to the street line or placed on a second line. The usual markers are Apt for an apartment, Ste for commercial space, Unit, Fl for floor, Bldg for building, and the bare #. Two conventions coexist: folding the unit into the street line (742 Evergreen Ter Apt 4B), or putting it on line two.

Both parse correctly, though a standardized record is cleaner with the unit in its own field. One practical note: some legacy systems truncate everything after a #, so spelling out Apt or Unit avoids that bug.

4. States always use two official letters

State names in an address are always two uppercase letters. The set was defined by USPS and has been stable for decades; the abbreviations are not simple initials, and full state names are rejected in the state field. Pennsylvania is PA, not PN; Arizona is AZ, while AR belongs to Arkansas. A short reference table:

The five sales-tax-free states follow the same rule: Alaska AK, Delaware DE, Montana MT, New Hampshire NH, Oregon OR. A wrong abbreviation breaks the record even when city and ZIP are correct.

5. What the digits in a ZIP code mean

ZIP stands for Zone Improvement Plan, introduced in 1963, and consists of five digits. The first digit divides the country into ten broad areas, increasing from the northeast toward the west:

The second and third digits point to a sectional center facility, the fourth and fifth to a post office or carrier route. ZIP+4 extends this with a hyphen and four more digits, written 95113-1234, narrowing to a block or a single building. Five digits suffice for everyday forms; ZIP+4 is mainly for bulk mail.

Each state's ZIP ranges are assigned by USPS and do not overlap across state lines, so the leading digits usually reveal the state. For the tax-free states: Alaska 995–999, Delaware 197–199, Montana 590–599, New Hampshire 030–038, Oregon 970–979.

6. Writing conventions and PO Boxes

USPS recommends uppercase letters, minimal punctuation, and the state abbreviation sharing the last line with the ZIP, separated by one or two spaces rather than glued together as CA-95113. On the street line, prefer the standard abbreviations: ST for Street, AVE for Avenue, N for North.

A PO Box is a separate kind of delivery point, written PO Box 1234. It is an alternative to a street address, not an addition. Some commercial couriers will not deliver to a PO Box and require a street address, while in some small towns residents only receive mail at a PO Box.

7. Why hand-built addresses fail validation

Assemble a few correct-looking fragments, and the response may still be invalid address. The cause is rarely formatting — it is inconsistency between fields. USPS address matching cross-checks four things: the street name and its valid house number range, the city, the state and the ZIP. If any one disagrees, the record is not deliverable.

The usual mismatches:

• City does not match ZIP — the ZIP belongs to city A but the city field says B.
• State does not match ZIP — the ZIP falls in California while the state reads NV.
• House number out of range — the street exists, but the number is not in its numbering interval.
• Missing suffix or directional — Main St typed as Main, and the street cannot be located.
• Non-standard abbreviations — a three-letter state code, or an invented suffix.

Payment adds another layer: AVS, the Address Verification System. It compares only the numeric parts — house number and the first five (or all nine) digits of the ZIP — against the billing address on file with the issuer, and returns one letter. Y means both match, A only the address, Z only the ZIP, N neither, and U means the check is unsupported. Many merchants treat N and U as an automatic decline, which explains a lot of "the address looks fine but it keeps failing" cases.

So coherence depends on four layers agreeing: the street sits in the right city, the city in the right state, the state's ZIP range covers that code, and the house number falls inside the street's numbering interval.

8. A worked example

A complete US address:

Jordan Ellis
1428 W Cedar Ave Apt 3B
Denver, CO 80223
United States

Part by part:

• 1428 house number, W directional prefix (west), Cedar street name, Ave street type suffix.
• Apt 3B unit designator, appended to the street line.
• Denver city, CO the official Colorado abbreviation, 80223 a five-digit ZIP whose leading 8 covers the Mountain states.
• United States the country line, needed only for international mail.

For a commercial address, the second line becomes Suite 200; for mail-only delivery, the street line can be replaced by PO Box 4412.

The US address generator on this site organizes its data by these rules: state paired with its official abbreviation, city paired with its ZIP, street suffixes and directionals in place. The records follow the format of real US addresses and are built from public geographic information, but they do not correspond to any real household — use them as format samples, form test data or UI demo material. To browse by state, start from the homepage.