What is dialing code from a mobile in UK to mobile in Toronto?

Canada is part of country code +1, so dial +1 and then the area code and number. Toronto uses area codes +1 416 and +1 647, with +1 437 to be added in 2013. The Toronto suburbs use area codes +1 905 and +1 289, with +1 365 also to be added in 2013.

From a GSM mobile phone, just program the number beginning with the plus sign; for example, +14165550123.