US Address Format — How to Write American Addresses Correctly

Whether you are mailing a letter, filling out an online form, or formatting addresses in a database, getting the US address format right matters. The United States Postal Service (USPS) has specific guidelines that ensure efficient mail delivery. This guide covers the standard format, apartment handling, all 50 state abbreviations, ZIP code rules, and common mistakes to avoid.

Standard US Address Format

A typical US address has three lines:

The USPS recommends uppercase letters with no punctuation for machine readability, but mixed case with commas is widely accepted for personal and business correspondence.

Line-by-Line Breakdown

Apartment, Suite, and Unit Formatting

If the recipient lives in an apartment, condo, or suite, include the unit designator on the same line as the street address:

If the street address line becomes too long, place the apartment designation on a separate line directly above the street address:

Accepted unit designators:

• APT — Apartment
• STE — Suite
• UNIT — Unit
• FL — Floor
• RM — Room
• # — Generic unit number (e.g., # 5A)

State Abbreviations — All 50 States

The USPS uses standard two-letter abbreviations for all states. Always use these in addresses — never spell out the full state name on mail.

Also note these common territories and districts:

• DC — District of Columbia
• PR — Puerto Rico
• GU — Guam
• VI — U.S. Virgin Islands
• AS — American Samoa

ZIP Code Format

5-Digit ZIP Code

The standard ZIP code is 5 digits. It identifies a general delivery area — typically a city, town, or portion of a metropolitan area.

ZIP+4 Code

ZIP+4 adds a hyphen and four additional digits to the standard ZIP code. The extra digits narrow the delivery to a specific city block, building, group of apartments, or individual high-volume receiver.

ZIP+4 is optional but recommended — it speeds up mail sorting and improves delivery accuracy.

USPS Formatting Rules

• Use uppercase letters for best machine readability (mixed case is acceptable for non-USPS forms)
• No punctuation — no periods, commas, or hyphens in the address lines (except the ZIP+4 hyphen)
• Put the city, state, and ZIP on the last line
• Use standard USPS abbreviations for street types: ST (Street), AVE (Avenue), BLVD (Boulevard), DR (Drive), CT (Court), LN (Lane), RD (Road), PL (Place)
• Use directional abbreviations: N (North), S (South), E (East), W (West), NE, NW, SE, SW
• Place one space between the state abbreviation and ZIP code

Common Mistakes

• Wrong state abbreviation — "MI" is Michigan, not Minnesota (which is "MN"). "MS" is Mississippi, not Missouri ("MO").
• Missing apartment number — if the recipient is in a multi-unit building, mail without a unit number may be returned
• City/ZIP mismatch — the ZIP code must match the city. Using the wrong ZIP code causes delays or returned mail
• Spelling out the state — USPS machines expect 2-letter abbreviations for optimal processing
• Putting the country on domestic mail — do not add "USA" or "United States" when mailing within the US

Mailing to the US from Another Country

When sending mail to the US from abroad, add UNITED STATES OF AMERICA (or USA) as the last line of the address:

Everything else remains the same — recipient, street, city/state/ZIP. The country name should be in the language of the origin country's postal service or in English.

Frequently Asked Questions