Current postage rates for Canada can be found in the United States Postal Service website or the CurrentPostageRates.org website. The USPS site has a "Quick Tools" tab to "Calculate a Price" where the customer selects the type of mail and "Canada" as destination, among other options, to calculate the postage.
CurrentPostageRates.org shows current postage rates for letters to Canada in a chart, which is very handy to use. The site claims to always show current postage rates. As of July 2015, regular envelopes less than two ounces in weight cost $1.20 while three ounce envelopes cost $1.67. Large envelopes cost more starting at $2.38 for a one ounce envelope up to $7.31 for an eight ounce large envelope.
In the USPS website, the postage for a specific size and weight of a letter needs to be calculated using the Postage Price Calculator. However, CurrentPostageRates.org does not offer information on postage rates for a postcard, express mail, small parcels or packages.
The USPS has strict size and weight limits for shipping packages to Canada. The maximum for First Class packages is four pounds. Anything over 66 pounds is shipped by Priority Mail Express. Though delivery times with USPS are longer than other delivery services, the cost by shipping via USPS flat rate boxes is about 50 percent cheaper, according to SmallBusiness.Chron.com.