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ZIP Code Format Guide
Complete guide to US ZIP code formats, rules, and USPS addressing standards.
5-Digit ZIP Code (Standard)
The standard ZIP code is a 5-digit number (e.g., 10001). Introduced in 1963, ZIP stands for "Zone Improvement Plan." The first digit represents a national area, the next two a sectional center facility, and the final two a local post office or delivery area.
10001— New York, NY
ZIP+4 (Extended ZIP Code)
The ZIP+4 code adds a hyphen and 4 additional digits after the 5-digit base (e.g., 10001-0001). The +4 identifies a specific city block, floor, or group of mailboxes. Required for bulk mailing and improves delivery speed.
10001-0001— Specific delivery point
Delivery Point Code (11 digits)
The full 11-digit code includes the 5-digit ZIP, the 4-digit extension, and a 2-digit delivery point code. Used internally by USPS equipment for automated sorting.
10001-0001-01— Full delivery point barcode
📋 USPS ZIP Code Rules
- →Always use 5 digits — pad with leading zeros if needed (e.g., 01234, not 1234)
- →ZIP codes run from 00501 (Holtsville, NY) to 99950 (Ketchikan, AK)
- →Write the city, state, and ZIP on the same line in USPS format
- →Use UPPERCASE for all address elements in printed mail
- →Leave two spaces between state abbreviation and ZIP code
- →USPS prefers the ZIP+4 format for business mail
- →Never use punctuation within the ZIP code itself
- →Military ZIP codes (APO/FPO/DPO) follow the same 5-digit format
✉️ Example USPS Address Format
JOHN SMITH
123 MAIN ST APT 4B
NEW YORK NY 10001-0001