Key takeaways
- Use a recipient line, a delivery address line, and a final city, state, and ZIP Code line
- Keep apartment or suite information with the delivery address, using a recognized unit designator
- Store state abbreviations and ZIP Codes as text so leading zeros are preserved
- Treat formatting, standardization, and delivery verification as separate checks
Authorship and review
Read our editorial and review principles- Written by
- Random Address Generator Editorial Team
- Reviewed by
- US Address Format Review Team
- Latest substantive update
- Published a US mailing address guide based on the October 2024 edition of USPS Publication 28, with examples for forms, apartment units, and ZIP+4 testing.
What is the standard US address format?
A standard US mailing address moves from the recipient to the delivery location, then ends with the city, two-letter state abbreviation, and ZIP Code. USPS Publication 28 describes three basic lines for a consumer address: the recipient line, the delivery address line, and the last line.
For domestic mail, do not add United States beneath the city, state, and ZIP Code. Add the country name only when the address is being written for international mail entering the United States.
US mailing address field order
Online forms often split the same mailing block into separate fields. Keep the original user input, then create a normalized mailing representation after validation. Address Line 2 must remain optional because many addresses have no apartment, suite, floor, or building value.
A five-digit ZIP Code can begin with zero, so it must be stored as text. The same rule applies to ZIP+4 because the hyphen is part of the displayed format.
| Form field | Example | Implementation note |
|---|---|---|
| Full name or organization | Alex Morgan | Keep recipient data separate from the street address |
| Address Line 1 | 225 N Humphreys Blvd | Primary number, directional, street name, and suffix |
| Address Line 2 | Suite 501 | Optional secondary unit; do not fill it with N/A |
| City | Memphis | Use the city value returned by an authorized address source |
| State | TN | Store the USPS two-letter abbreviation, not a guessed value |
| ZIP Code | 38188-1001 | Store as text and preserve a valid ZIP+4 hyphen |
| Country code | US | Use ISO code US in data; show United States in international output |
How do apartments and suites fit in a US address?
USPS calls an apartment, suite, room, floor, department, or unit a secondary address element. When space allows, place the approved designator and unit identifier at the end of the delivery address line. Examples include APT 4B, STE 501, FL 2, RM 210, and UNIT 7.
If the complete delivery address cannot fit on one line, put the secondary unit line immediately above the street delivery line. Do not drop the unit number during normalization because it may distinguish one delivery point from every other unit in the building.
- Accept common user input such as Apartment 4B, then normalize only for mailing output
- Keep unit designator and unit identifier in separate database fields when possible
- Do not require Address Line 2 for single-unit buildings
- Test long street names and unit values before setting form length limits
How to write the city, state, and ZIP Code line
The last line places the city first, followed by the two-letter state abbreviation and ZIP Code. A comma between city and state is common in everyday writing, but punctuation is not needed for USPS automation output. The important part is keeping the city, state, and ZIP Code on one line when possible.
A ZIP Code identifies a postal delivery area, not a state by itself. Some ZIP Codes serve military, federal, or special-purpose destinations. Do not infer a complete address from a ZIP Code alone, and do not claim deliverability unless a current USPS or licensed address-validation result confirms it.
| Input | Mailing output | Test |
|---|---|---|
| Boston, Massachusetts 02108 | BOSTON MA 02108 | Normalize the state name to MA and preserve the leading zero |
| Memphis TN 38188 1001 | MEMPHIS TN 38188-1001 | Insert the ZIP+4 hyphen only after validating the digits |
| New York, NY 10001 | NEW YORK NY 10001 | Keep a multiword city intact |
How to write an American address on an envelope
Place the delivery address in the center of the envelope and the return address in the upper-left corner. Use a uniform left margin for the address block. Machine-printed uppercase text is the USPS preference for automation-readable mail, but mixed case remains normal in online forms and human-readable interfaces.
Keep nonaddress instructions outside the delivery address block. If you have both a street address and a PO Box, the address immediately above the city, state, and ZIP Code is treated as the intended delivery address.
- Recipient or organization on the first line
- Street and unit information on the delivery line
- City, state abbreviation, and ZIP Code on the final domestic line
- UNITED STATES on a separate final line only for international mail
How should a US address form validate each field?
Good form validation checks whether fields are present and shaped correctly without pretending that formatting proves a delivery point exists. A browser can check a two-letter state code and the five-digit or ZIP+4 pattern. A server can normalize whitespace and known abbreviations. Delivery verification needs a current authoritative service.
Do not silently replace user input before showing the proposed correction. Keep the original value for support and audit work, and store normalized values separately. This makes it possible to distinguish what the user entered from what an address service returned.
| Layer | What it can confirm | What it cannot confirm |
|---|---|---|
| Client-side format | Required fields, state code shape, ZIP pattern | That the street or unit exists |
| Normalization | Whitespace, casing, suffix and unit conventions | That mail can be delivered |
| Address validation service | A current match and suggested standardized address | That a recipient lives or works there |
US address test cases worth keeping
A useful test set includes ordinary addresses plus cases that break number fields, fixed line counts, and state assumptions. Keep fixtures labeled as synthetic or public non-residential data, and never use generated records for shipping, payment, credit, identity, or account verification.
- A Northeast ZIP Code with a leading zero
- A ZIP+4 value with the required hyphen
- An apartment or suite on the delivery line
- A long unit value that wraps above the street line
- A PO Box and a street address stored as separate delivery choices
- A multiword city such as New York or Salt Lake City
- A military or territory address handled by its specific USPS rules
- A syntactically valid address that receives no delivery-validation match
Frequently asked questions
What is an example of a correctly formatted US address?
Use three basic lines: ALEX MORGAN, then 225 N HUMPHREYS BLVD STE 501, then MEMPHIS TN 38188-1001. The name is synthetic and the location is a public USPS office address used here only to explain the format.
Do I put a comma between the city and state?
A comma is common in normal writing, such as Memphis, TN 38188. USPS automation output does not require punctuation, so MEMPHIS TN 38188 is also correct for a mailpiece.
Does the apartment number go on Address Line 2?
It can. Online forms often provide Address Line 2 for the apartment or suite. On a mailpiece, USPS prefers the unit designator and number at the end of the delivery line when they fit.
Should a US ZIP Code be stored as a number?
No. Store it as text so leading zeros remain intact and ZIP+4 values can keep their hyphen.
How do I write a US address from another country?
Use the normal recipient, delivery, and city-state-ZIP lines, then add UNITED STATES on its own final line. Do not put the country line on domestic US mail.
Does correct formatting prove an address is deliverable?
No. Correct line order and field shapes only confirm format. Use USPS ZIP Code Lookup or an authorized address-validation service for a current delivery match.