US Area Codes and Phone Number Format Explained
US phone numbers follow the North American Numbering Plan. Every number has ten digits, split into three parts.
The three parts
- Area code: three digits that identify a geographic region, such as 212 for Manhattan.
- Exchange (central office code): three digits.
- Line number: four digits.
Written out: (212) 555-0147 or 212-555-0147, and +1 212 555 0147 internationally.
Overlay area codes
When a region runs out of numbers, a new area code is often added on top of the existing one instead of splitting the region. That is why New York City has 212, 646, 332 and 917 serving the same streets, and why ten-digit dialing is now required in most places.
Why test numbers use 555-01XX
The numbers 555-0100 through 555-0199 are reserved for fictional use in every area code. They will not ring a real person. Our generator uses this range with a real local area code, so numbers look realistic but are safe to use in demos, test data and screenshots.
Formatting for storage
Store phone numbers as text in E.164 format (+12125550147) and format them for display. This keeps sorting, searching and international support simple.
Testing phone fields
Test with parentheses, dashes, spaces and the +1 prefix. A good form accepts all of them and normalizes the input before saving.
Generate realistic US addresses for forms, databases and design mockups, then copy or download them as CSV or JSON.
Open the address generator