After January 24th, 2021 you'll need $1.15 in postage to mail any of the following first-class letters:
- 1st class, 3 oz - odd size letters
- 1st class, 3.5 oz
a letter that weighs 3 oz but is also odd-sized/non-machinable
This weight/size combination is quite rare but the post office does have a rate for it.
There are no stamps with a face value for this specific rate. If you want to use stamps you'll need to combine stamps with a smaller face value to add up to $1.15 or greater.
You can determine if your wedding invitation is a standard letter or a large envelope by using our postage calculator, but be sure to double-check the weight of your invitations with your local USPS post office before ordering postage online.