Currently, postage for rectangular envelopes is $0.49 and $0.70 for square envelopes – both weighing up to 1 ounce. An ounce usually consists of one card or invitation and an RSVP or one booklet card with a RSVP. If you include more than that in your envelope, you may need to purchase more postage. For up-to-date postage pricing, please visit