What is the most popular Flyer size? January 09, 2014 16:55 Follow The most common flyer size is 4 x 6 inches (in North America). This is the size of a standard postcard. Related articles What size is a Rack Card? What size are Postcards? Do you offer your pre-made designs in other languages? Can I upload more than 1 design on a single order? How do I apply food safe stickers?