Square envelope postage
If you are mailing square wedding invitations you may be in for a surprise—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 $0.21 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 $0.68 stamp (instead of a $0.47 stamp) and for wedding invitations that weigh 2oz you'll need a $0.89 stamp (instead of a $0.68 stamp). For help in determining the exact postage rate you need you can use our postage calculator.
(Making your own square invitations? Remember the minimum size of a square envelope is 5" x 5" in order to be delivered by the USPS.)
Odd-Size/Nonmachineable Letters
Square letters are considered odd-sized/nonmachineable. Here are some other factors that will result in you paying a postage surcharge:
- envelopes that are too rigid
- envelopes that don't bend easily
- envelopes that are more than 1/4" thick
- envelopes that have clasps, strings, or other non-standard closures
Typically the postal service will only charge one surcharge even if your mailpiece has two nonmachineable characteristics (such as a square envelope with a clasp). However, be sure to visit your local post office so they can help you determine the exact amount of postage you'll need to mail your letter.
