Telephone numbers in Canada follow the fixed-length Bell System format, consisting of the country code +1, followed by a three-digit area code, a three-digit central office code (or exchange code) and a four-digit station code. This is represented as 1 NPA NXX XXXX, in which the country code is "1".
Local calls from Canadian landlines must be dialled without the leading '1', which is used as the trunk prefix for domestic long-distance calls. Toll calls from Canada to other North American Numbering Plan countries are dialled in the same format (eleven digits) as domestic calls. Overseas calls to locations outside country code +1 are dialled with the 011 international prefix, followed by the country code and the national significant number.
From : Wiki