in what country usa? usa:39 cents
The cost of postage depends on how much it weighs and the country where you are mailing it and its destination.
$.78
how much postage required for a 9x12 envelope weighing 4.6 ounces
how much postage for a 9x12 envelope weighing 6.6 ounces
Calculate it on usps.com
3
If it's just got a few photos it is 1.39
one stamp is good for one ounce. packaged by weight not by volume. Size doesn't matter.
Those dimensions make it a large envelope, so postage starts at 94 cents (two Forever stamps) for the first ounce, and more if it's heavier.
9x12 feet at 4 inches deep: 1.3 cubic yards.
a 7x9 mailer weighs roughly 1.5 ounces