The fast-growing areas surrounding Canada's largest city will get a new area code starting in 2013.

The area around Toronto is known colloquially as "the 905," after the area code that was added in 1993 and covers such areas as Mississauga and Niagara Falls.

The 289 area code was overlaid over the 905 in 2001 and the CRTC announced Tuesday the new 365 code will make its debut in March 2013.

The move was necessary because Toronto's suburbs are rapidly gobbling up the available phone numbers of existing area codes. Without the new 365 code, the region would have run out of numbers by about 2014.

The CRTC says the growing need for numbers is fuelled not only by population growth but also by cellphone use.

"There's more and more people using more and more devices," said CRTC spokesperson Denis Carmel. "When I was a kid, every family had one number. Now we all have about 12."

Another factor is the growth in the number of telecommunication providers in Canada. The CRTC assigns large blocks of numbers at a time to providers, putting pressure on the total amount of numbers available.

And while the new area code helps relieve the Greater Toronto Area's number pressure for now, it really only buys time. The region is expected to add another area code — the 742 — in about 14 years.

Because Canada shares its area codes with those in the United States, eventually the number of available area codes will be exhausted. For this reason, Carmel said North America is likely headed for 12-digit dialing by 2039.