NANP

The North American Numbering Plan (NANP) is a telephone numbering system used by the United States, Canada, Bermuda, and many Caribbean nations. It provides a single, unified framework for assigning telephone numbers and routing calls across participating countries and territories, while allowing local dialing within each area.

The NANP uses the E.164 numbering format and the country code +1. Within the NANP, a typical ten-digit number consists of a three‑digit area code (NPA), a three‑digit central office code (NXX), and a four‑digit line number. In domestic form, numbers are written as NPA-NXX-XXXX or, when dialing internationally, +1-NPA-NXX-XXXX. Local calls are often dialed with seven digits, while national or international calls require the 1 prefix or the country’s international access code.

Numbering rules impose restrictions to preserve dial plan integrity. The first digit of both an area code and a central office code is restricted to 2 through 9. N11 dialing patterns (such as 211, 411, 511, 611, 811) are reserved for special services, and 911 is reserved for emergency use.

Administration and governance are handled by the North American Numbering Plan Administration (NANPA) under the oversight of regulators in the United States and Canada (the FCC and the CRTC). The administrator is typically a private company selected through a bidding process, responsible for number allocation, portability, and preventing exhaustion of area codes.

History and scope: the plan was introduced in 1947 to simplify long-distance calling and create a scalable numbering framework. It has since expanded to accommodate population growth and new services, with area-code relief implemented through splits and overlays as needed.