Some of the most populated postal codes in Ontario are M4C 1S6 (45,822), K1G 0M2 (33,994), L8E 2P2 (38,320), L6P 0P3 (61,932) and L4T 1N7 (39,097), as of 2015. Each of these postal codes lies within Toronto, Ottawa, Hamilton, Brampton and Mississauga, respectively, which are the largest cities in Ontario.
Toronto, the largest city in Ontario, has a population of 2,615,060. Ottawa represents the second-largest city in the province, with a population of 883,391. Mississauga is third with 713,443, Brampton fourth with 523,911 and Hamilton fifth with 519,949 people . Each of the five aforementioned cities contains 400 postal codes.