//10-digit phone number
^(?:\+?1\s*(?:[.-]\s*)?)?(?:\(\s*([2-9]1[02-9]|[2-9][02-8]1|[2-9][02-8][02-9])\s*\)|([2-9]1[02-9]|[2-9][02-8]1|[2-9][02-8][02-9]))\s*(?:[.-]\s*)?([2-9]1[02-9]|[2-9][02-9]1|[2-9][02-9]{2})\s*(?:[.-]\s*)?([0-9]{4})$

//10-digit phone number, extension allowed
^(?:\+?1\s*(?:[.-]\s*)?)?(?:\(\s*([2-9]1[02-9]|[2-9][02-8]1|[2-9][02-8][02-9])\s*\)|([2-9]1[02-9]|[2-9][02-8]1|[2-9][02-8][02-9]))\s*(?:[.-]\s*)?([2-9]1[02-9]|[2-9][02-9]1|[2-9][02-9]{2})\s*(?:[.-]\s*)?([0-9]{4})(?:\s*(?:#|x\.?|ext\.?|extension)\s*(\d+))?$

//7 or 10-digit phone number
^(?:(?:\+?1\s*(?:[.-]\s*)?)?(?:\(\s*([2-9]1[02-9]|[2-9][02-8]1|[2-9][02-8][02-9])\s*\)|([2-9]1[02-9]|[2-9][02-8]1|[2-9][02-8][02-9]))\s*(?:[.-]\s*)?)?([2-9]1[02-9]|[2-9][02-9]1|[2-9][02-9]{2})\s*(?:[.-]\s*)?([0-9]{4})$

//7 or 10-digit phone number, extension allowed
^(?:(?:\+?1\s*(?:[.-]\s*)?)?(?:\(\s*([2-9]1[02-9]|[2-9][02-8]1|[2-9][02-8][02-9])\s*\)|([2-9]1[02-9]|[2-9][02-8]1|[2-9][02-8][02-9]))\s*(?:[.-]\s*)?)?([2-9]1[02-9]|[2-9][02-9]1|[2-9][02-9]{2})\s*(?:[.-]\s*)?([0-9]{4})(?:\s*(?:#|x\.?|ext\.?|extension)\s*(\d+))?$

//10-digit phone number, vanity (alphanumeric) allowed
^(?:\+?1\s*(?:[.-]\s*)?)?(?:\(\s*([2-9]1[02-9]|[2-9][02-8]1|[2-9][02-8][02-9])\s*\)|([2-9]1[02-9]|[2-9][02-8]1|[2-9][02-8][02-9]))\s*(?:[.-]\s*)?([2-9a-z]1[02-9a-z]|[2-9a-z][02-9a-z]1|[2-9a-z][02-9a-z]{2})([0-9a-z]{4})$

//10-digit phone number, vanity allowed, extra characters allowed at end
^(?:\+?1\s*(?:[.-]\s*)?)?(?:\(\s*([2-9]1[02-9]|[2-9][02-8]1|[2-9][02-8][02-9])\s*\)|([2-9]1[02-9]|[2-9][02-8]1|[2-9][02-8][02-9]))\s*(?:[.-]\s*)?([2-9a-z]1[02-9a-z]|[2-9a-z][02-9a-z]1|[2-9a-z][02-9a-z]{2})([0-9a-z]{4})([0-9a-z]*)$

//10-digit phone number
^(?:\+?1\s*(?:[.-]\s*)?)?(?:\(\s*([2-9]1[02-9]|[2-9][02-8]1|[2-9][02-8][02-9])\s*\)|([2-9]1[02-9]|[2-9][02-8]1|[2-9][02-8][02-9]))\s*(?:[.-]\s*)?([2-9]1[02-9]|[2-9][02-9]1|[2-9][02-9]{2})\s*(?:[.-]\s*)?([0-9]{4})$

//10-digit phone number, extension allowed
^(?:\+?1\s*(?:[.-]\s*)?)?(?:\(\s*([2-9]1[02-9]|[2-9][02-8]1|[2-9][02-8][02-9])\s*\)|([2-9]1[02-9]|[2-9][02-8]1|[2-9][02-8][02-9]))\s*(?:[.-]\s*)?([2-9]1[02-9]|[2-9][02-9]1|[2-9][02-9]{2})\s*(?:[.-]\s*)?([0-9]{4})(?:\s*(?:#|x\.?|ext\.?|extension)\s*(\d+))?$

//7 or 10-digit phone number
^(?:(?:\+?1\s*(?:[.-]\s*)?)?(?:\(\s*([2-9]1[02-9]|[2-9][02-8]1|[2-9][02-8][02-9])\s*\)|([2-9]1[02-9]|[2-9][02-8]1|[2-9][02-8][02-9]))\s*(?:[.-]\s*)?)?([2-9]1[02-9]|[2-9][02-9]1|[2-9][02-9]{2})\s*(?:[.-]\s*)?([0-9]{4})$

//7 or 10-digit phone number, extension allowed
^(?:(?:\+?1\s*(?:[.-]\s*)?)?(?:\(\s*([2-9]1[02-9]|[2-9][02-8]1|[2-9][02-8][02-9])\s*\)|([2-9]1[02-9]|[2-9][02-8]1|[2-9][02-8][02-9]))\s*(?:[.-]\s*)?)?([2-9]1[02-9]|[2-9][02-9]1|[2-9][02-9]{2})\s*(?:[.-]\s*)?([0-9]{4})(?:\s*(?:#|x\.?|ext\.?|extension)\s*(\d+))?$

//10-digit phone number, vanity (alphanumeric) allowed
^(?:\+?1\s*(?:[.-]\s*)?)?(?:\(\s*([2-9]1[02-9]|[2-9][02-8]1|[2-9][02-8][02-9])\s*\)|([2-9]1[02-9]|[2-9][02-8]1|[2-9][02-8][02-9]))\s*(?:[.-]\s*)?([2-9a-z]1[02-9a-z]|[2-9a-z][02-9a-z]1|[2-9a-z][02-9a-z]{2})([0-9a-z]{4})$

//10-digit phone number, vanity allowed, extra characters allowed at end of number
^(?:\+?1\s*(?:[.-]\s*)?)?(?:\(\s*([2-9]1[02-9]|[2-9][02-8]1|[2-9][02-8][02-9])\s*\)|([2-9]1[02-9]|[2-9][02-8]1|[2-9][02-8][02-9]))\s*(?:[.-]\s*)?([2-9a-z]1[02-9a-z]|[2-9a-z][02-9a-z]1|[2-9a-z][02-9a-z]{2})([0-9a-z]{4})([0-9a-z]*)$

//10-digit phone number
^(?:\+?1\s*[.-]?\s*)?(?:\(\s*([2-9]1[02-9]|[2-9][02-8]1|[2-9][02-8][02-9])\s*\)|([2-9]1[02-9]|[2-9][02-8]1|[2-9][02-8][02-9]))\s*[.-]?\s*([2-9]1[02-9]|[2-9][02-9]1|[2-9][02-9]{2})\s*[.-]?\s*([0-9]{4})$

//10-digit phone number, extension allowed
^(?:\+?1\s*[.-]?\s*)?(?:\(\s*([2-9]1[02-9]|[2-9][02-8]1|[2-9][02-8][02-9])\s*\)|([2-9]1[02-9]|[2-9][02-8]1|[2-9][02-8][02-9]))\s*[.-]?\s*([2-9]1[02-9]|[2-9][02-9]1|[2-9][02-9]{2})\s*[.-]?\s*([0-9]{4})(?:\s*(?:#|x\.?|ext\.?|extension)\s*(\d+))?$

//7 or 10-digit phone number
^(?:(?:\+?1\s*[.-]?\s*)?(?:\(\s*([2-9]1[02-9]|[2-9][02-8]1|[2-9][02-8][02-9])\s*\)|([2-9]1[02-9]|[2-9][02-8]1|[2-9][02-8][02-9]))\s*[.-]?\s*)?([2-9]1[02-9]|[2-9][02-9]1|[2-9][02-9]{2})\s*[.-]?\s*([0-9]{4})$

//7 or 10-digit phone number, extension allowed
^(?:(?:\+?1\s*[.-]?\s*)?(?:\(\s*([2-9]1[02-9]|[2-9][02-8]1|[2-9][02-8][02-9])\s*\)|([2-9]1[02-9]|[2-9][02-8]1|[2-9][02-8][02-9]))\s*[.-]?\s*)?([2-9]1[02-9]|[2-9][02-9]1|[2-9][02-9]{2})\s*[.-]?\s*([0-9]{4})(?:\s*(?:#|x\.?|ext\.?|extension)\s*(\d+))?$

//10-digit phone number, vanity (alphanumeric) allowed
^(?:\+?1\s*[.-]?\s*)?(?:\(\s*([2-9]1[02-9]|[2-9][02-8]1|[2-9][02-8][02-9])\s*\)|([2-9]1[02-9]|[2-9][02-8]1|[2-9][02-8][02-9]))\s*[.-]?\s*([2-9a-z]1[02-9a-z]|[2-9a-z][02-9a-z]1|[2-9a-z][02-9a-z]{2})\s*[.-]?\s*([0-9a-z]{4})$

//10-digit phone number, vanity allowed, extra characters allowed at end of number
^(?:\+?1\s*[.-]?\s*)?(?:\(\s*([2-9]1[02-9]|[2-9][02-8]1|[2-9][02-8][02-9])\s*\)|([2-9]1[02-9]|[2-9][02-8]1|[2-9][02-8][02-9]))\s*[.-]?\s*([2-9a-z]1[02-9a-z]|[2-9a-z][02-9a-z]1|[2-9a-z][02-9a-z]{2})\s*[.-]?\s*([0-9a-z]{4})(?:\s*([0-9a-z]+))?$

//10-digit phone number
^(?:\+?1\s*[.-]?\s*)?(?:\(\s*([2-9]1[0,2-9]|[2-9][0,2-8]1|[2-9][0,2-8][0,2-9])\s*\)|([2-9]1[0,2-9]|[2-9][0,2-8]1|[2-9][0,2-8][0,2-9]))\s*[.-]?\s*([2-9]1[0,2-9]|[2-9][0,2-9]1|[2-9][0,2-9]{2})\s*[.-]?\s*([0-9]{4})$

//10-digit phone number, extension allowed
^(?:\+?1\s*[.-]?\s*)?(?:\(\s*([2-9]1[0,2-9]|[2-9][0,2-8]1|[2-9][0,2-8][0,2-9])\s*\)|([2-9]1[0,2-9]|[2-9][0,2-8]1|[2-9][0,2-8][0,2-9]))\s*[.-]?\s*([2-9]1[0,2-9]|[2-9][0,2-9]1|[2-9][0,2-9]{2})\s*[.-]?\s*([0-9]{4})(?:\s*(?:#|x\.?|ext\.?|extension)\s*(\d+))?$

//7 or 10-digit phone number
^(?:(?:\+?1\s*[.-]?\s*)?(?:\(\s*([2-9]1[0,2-9]|[2-9][0,2-8]1|[2-9][0,2-8][0,2-9])\s*\)|([2-9]1[0,2-9]|[2-9][0,2-8]1|[2-9][0,2-8][0,2-9]))\s*[.-]?\s*)?([2-9]1[0,2-9]|[2-9][0,2-9]1|[2-9][0,2-9]{2})\s*[.-]?\s*([0-9]{4})$

//7 or 10-digit phone number, extension allowed
^(?:(?:\+?1\s*[.-]?\s*)?(?:\(\s*([2-9]1[0,2-9]|[2-9][0,2-8]1|[2-9][0,2-8][0,2-9])\s*\)|([2-9]1[0,2-9]|[2-9][0,2-8]1|[2-9][0,2-8][0,2-9]))\s*[.-]?\s*)?([2-9]1[0,2-9]|[2-9][0,2-9]1|[2-9][0,2-9]{2})\s*[.-]?\s*([0-9]{4})(?:\s*(?:#|x\.?|ext\.?|extension)\s*(\d+))?$

//10-digit phone number, vanity (alphanumeric) allowed
^(?:\+?1\s*[.-]?\s*)?(?:\(\s*([2-9]1[0,2-9]|[2-9][0,2-8]1|[2-9][0,2-8][0,2-9])\s*\)|([2-9]1[0,2-9]|[2-9][0,2-8]1|[2-9][0,2-8][0,2-9]))\s*[.-]?\s*([2-9a-z]1[0,2-9a-z]|[2-9a-z][0,2-9a-z]1|[2-9a-z][0,2-9a-z]{2})\s*[.-]?\s*([0-9a-z]{4})$

//10-digit phone number, vanity allowed, extra characters allowed at end of number
^(?:\+?1\s*[.-]?\s*)?(?:\(\s*([2-9]1[0,2-9]|[2-9][0,2-8]1|[2-9][0,2-8][0,2-9])\s*\)|([2-9]1[0,2-9]|[2-9][0,2-8]1|[2-9][0,2-8][0,2-9]))\s*[.-]?\s*([2-9a-z]1[0,2-9a-z]|[2-9a-z][0,2-9a-z]1|[2-9a-z][0,2-9a-z]{2})\s*[.-]?\s*([0-9a-z]{4})(?:\s*([0-9a-z]+))?$

http://en.wikipedia.org/wiki/North_American_Numbering_Plan

(Created for JavaScript)

These are rather forgiving. Spaces, dashes, or periods are allowed as separators. Extensions can be recognized by several strings (#, x, x., ext, ext., extension).

Area code: $1$2  
Exchange code: $3  
Station code: $4  
Extension / Extra characters: $5

Separators are not accepted within the $3$4$5 portion of a vanity number.

Example: (540) 555-0123 ext.678 --> `($1$2) $3-$4 ext.$5`  
Example: 1-800-GOODFOOD --> `1-$1$2-$3$4$5`

Regular Expressions for U.S. Phone Numbers

regex, javascript, phone

Regular Expression