Phone Number Format Guide

Formats & Generator

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US Phone Number Format Guide and Examples

Dial Code: +1•Last updated: January 1, 2026

Local Format
(555) 123-4567
E.164 Format
+15551234567
International
+1 555 123 4567

About United States Phone Numbers

US phone numbers consist of 10 digits, typically formatted as (XXX) XXX-XXXX. The first 3 digits are the area code. Mobile and landline numbers share the same format.

How to Dial United States Phone Numbers

To call a US phone number, the exact format depends on where the call starts. Most domestic calls use the full 10-digit number, while international calls to the US use the +1 country code.

  • Within the US: Most calls use the full 10-digit number without adding +1.
    Example: 2125550123
  • From abroad to the US: Dial +1 followed by the 10-digit US number.
    Example: +1 212 555 0123
  • From the US to other countries: Dial 011, then the country code, then the full phone number.
    Example: 011 44 20 7946 0958

Note: US national numbers usually contain a 3-digit area code and a 7-digit local number.

Phone Number Structure

This table breaks down the example number shown for United States.

ComponentDigitsExampleNotes
Country Code1+1Shared across the North American Numbering Plan and omitted in standard domestic 10-digit dialing.
Area Code3555Identifies the numbering plan area for the number.
Central Office Code3123Also called the prefix or exchange; this is the middle block of a NANP number.
Line Number44567Identifies the individual subscriber line within the central office code.

Special Cases

Some numbers and prefixes in United States have special rules or reserved uses.

  • 555 Fictional Numbers

    555555-0100 to 555-0199

    Numbers in the 555-0100 through 555-0199 range are commonly reserved for fictional use in film, television, and other media to avoid reaching real subscribers.

  • Emergency Services (911)

    911

    911 is the nationwide emergency number in the United States. Regular telephone numbers are not assigned with 911 as a standard prefix in the way ordinary geographic numbers are structured.

  • Toll-Free Numbers

    800888877866855844833

    These prefixes typically indicate toll-free services, which means callers in the US are generally not charged for the call under standard billing arrangements.

Validation Regex

regexregex
^\(\d{3}\) \d{3}-\d{4}$|^\d{10}$|^\+1\d{10}$

Code Examples

CSS Masking Format

Use this CSS mask to automatically format phone number inputs:

cssinput-masking.css
input[type="tel"] {
  mask: (000) 000-0000;
  mask-image: none; /* Fallback */
}

Other Countries

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