The wedding season.

Google. You’ll find a lot info ( e.g. theamericanwedding.com, invitationswithstyle.com)

Oh yeah, Google. Thans for the links David.

CHeck with the post office. Then check with another. I made the mistake once of checking with one Post Office saying my postcards were just fine then finding out at another one that the postcards were two small and I’d instead have to use envelopes for them all.

As for wedding standards, I don’t think there really is one…they just adhere to standard greeting card/envelope sized.

Two important considerations:

1. ANYTHING smaller than 3.5”Hx5”W is NOT mailable.

2. Square invitations may look classy, but they’ll cost you an extra 12¢ apiece to mail (non-standard surcharge).

If you have ANY questions. contact your local USPS BMEU (Business Mail Entry Unit) and request a FREE Notice 3A: Letter-size Mail DImensional Standards Template.