How do you dial a telephone call from the United States to Canada?

The United States and Canada are both part of the North American Numbering Plan, an integrated telephone numbering system that also includes 18 island nations and territories in or near the Caribbean. Telephone numbers in the NANP consist of the telephone country code +1, an area code (always 3 digits) and a subscriber number (always 7 digits).

Calls within the NANP, including calls from the US to Canada or vice-versa, are dialed "one plus," the same as a domestic long distance call. For example, a call to Calgary, Alberta, (403) 555-0123 would be dialed simply as 1-403-555-0123.