I went to the USPS website and got the following information.
According to the USPS website you'll pay .33 (that's as of today, 2/14/13) to mail a postcard with a minimum size of 5" long by 3-1/2 " high by .007" thick to a maximum of 6" long by 4-1/4" inches high by .016 inch thick. International postcards just went up (January 2013) to a whopping $1.10. The good news is that there's now a Forever International Stamp so we can stock up before the next rate change. The bad news is that it now costs as much to send to Canada and Mexico as it does to Nepal.
Additional notes from the USPS site:
- Any item smaller than the minimum dimensions is not mailable
- For postcards, length is the dimension parallel to the address
- Postcards must be rectangular and be made of unfolded and uncreased paper or card stock.
- Large cards that exceed the maximum dimensions of a postcard pay the First-Class Mail letter, large envelope, or package price
Please download the blank postcard template here in pdf format.