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North America · +1

United States phone number format

  • Country code +1
  • No trunk prefix

Reviewed by Sujan ThapaliyaLast updated

What does a United States phone number look like?

10 digits: a 3-digit area code plus a 7-digit subscriber number. Landlines are written +1 (NPA) NXX-XXXX and mobiles +1 (NPA) NXX-XXXX (same format as landline). In full international (E.164) format a United States mobile is written +12125550187: the country code +1, and no spaces or punctuation.
The anatomy of a United States phone number under ITU-T E.164: country calling code 1, then the national destination code, then the subscriber number, to a maximum of fifteen digits after the plus. Nationally a United States number is written +1 (NPA) NXX-XXXX; in E.164 the prefix and the spacing both come off.
National formatting is for people. E.164 is for databases, APIs, and caller ID — store United States numbers in the right-hand form.

Format rules

Country code
+1
National number length
10 digits: a 3-digit area code plus a 7-digit subscriber number
Trunk prefix
None
The local number is already the international number.
Landline pattern
+1 (NPA) NXX-XXXX
Mobile pattern
+1 (NPA) NXX-XXXX (same format as landline)

Examples

United States phone number examples

555-0100 through 555-0199 are reserved for fictional use, so these examples never reach a real subscriber.

TypeWritten domesticallyInternational (E.164)
Landline(415) 555-0123+14155550123
Mobile(NPA) NXX-XXXX (same format as landline)+12125550187

A quirk of United States numbering

US mobile and landline numbers are indistinguishable by prefix; you cannot tell them apart without a carrier lookup.

Validation

How to validate a United States number

Validating a phone number is three separate checks, and conflating them is the usual source of bugs:

  1. Format: does it match the shape for United States? 10 digits: a 3-digit area code plus a 7-digit subscriber number, after the country code .
  2. Allocation: is the prefix actually in use? A number can be the right length and still belong to an unallocated range.
  3. Reachability: is there a live subscriber? Only a carrier lookup (HLR or equivalent) answers that, and it is the only check that catches disconnected numbers.

For form validation, check format only and be permissive: accept spaces, dashes, brackets, and a leading 0 then normalise. Rejecting a real customer because they typed their own number the way they normally write it is a far more expensive error than storing one badly formatted row.

Store in E.164 (+12125550187) and format for display at render time. Storing the display format is how a database ends up with the same person recorded four different ways.

Format any number instantly

Paste a number into the free phone number formatter to convert it to E.164 and see whether it matches United States’s format rules. No sign-up.

Frequently asked questions

What does a United States phone number look like?
10 digits: a 3-digit area code plus a 7-digit subscriber number. A landline is written +1 (NPA) NXX-XXXX and a mobile +1 (NPA) NXX-XXXX (same format as landline). In full international format that becomes +12125550187.
How do I write a United States number in international format?
Start with +1, then append the rest with no spaces or punctuation. +1 (415) 555-0123 becomes +14155550123.
How many digits is a United States phone number?
10 digits: a 3-digit area code plus a 7-digit subscriber number.
How do I tell a United States mobile from a landline?
By the prefix. Mobiles follow the pattern +1 (NPA) NXX-XXXX (same format as landline), while landlines follow +1 (NPA) NXX-XXXX.
Should I store phone numbers with the plus sign?
Yes. Store every number in E.164: leading +, country code, national number, no spaces or punctuation, up to 15 digits. It is the only format that is unambiguous internationally, and it is what makes deduplication work. Format for display, store canonical.

Sources

  1. ITU-T Recommendation E.164 — The international public telecommunication numbering plan — International Telecommunication UnionThe international number format, the 15-digit maximum, and how country codes and national numbers compose.
  2. ITU-T International Numbering Resources — International Telecommunication UnionThe assignment of country calling codes and the published national numbering plans they belong to.

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