There are 523 different postal code prefixes for Ontario, Canada. "ZIP code" is an American term that means roughly the same thing as postal code in Canada. All postal codes in Ontario begin with letters K, L, M, N or P.
The first three digits in a Canadian postal code determine to which Forwarding Sortation Area the mail is sent. A space follows the first three digits and then there are 3 other digits which determine the mail's exact destination. The top 5 postal code prefixes in Ontario are K0K, K0A, L4N, L5N and N0G. Most of these heavily populated codes are in rural areas, which encompass areas several times larger than the most populated codes in Toronto or other cities in Ontario.