do square invites cost more to send?
Postage for Square Envelopes. If you are mailing square wedding invitations you may be in for a surpriseâthe USPS imposes an additional surcharge for square envelopes. Letters that are square (height = width) are considered odd-sized or nonmachineable by the post office resulting in a higher price for postage. Square envelopes will cost you an extra $0.22 per letter in addition to the postage required for the weight and dimensions of your envelope. For 1 oz letters this means you'll need a $0.71 stamp (instead of a $0.49 stamp) and for wedding invitations that weigh 2oz you'll need a $0.93 stamp (instead of a $0.71 stamp).