You are able to customize a wedding invitation in various available sizes. Wedding Request SizesTo know what is the ideal size for the invitation which you have chosen, you must start with the accessible envelope sizes. Wedding Invitations Dimensions Once you recognized the envelope size that this invitation will be mailed within, then you can identify the right scale the invitation. You have 2 options in mailing your wedding day invitation. One is to email the invitation with external and inner envelopes to maintain the inner envelope of the request clean and good for souvenirs. Two is to mail the actual invitation in just one package and it is actually cost efficient to get this done.