What is the proper size for a postcard?
In order to get the “postcard” rates in First Class mail, the card must be at least 31/2 x 5 inches and cannot exceed 41/4 x 6. In Standard mail (the old Bulk Rate), there is no special recognition of a “card” in the rate structure. Cards and folded self-mailers go at the same rates. A folded self-mailer can be as big as 61/8 x 111/2 and still mail at the same rates as a 31/2 x 5 card. The aspect ratio described above should be met.
