1 If you send your invitations out 6 to 8 weeks in advance, the likelihood is that most of them will come. 2  So estimate that 85% of them will attend. 3  Don’t forget to account for plus ones, if you’ve invited them.4  Out of town acceptance rate is around 85% for family and 40% for friends. (# of out of town guests * 65%) + (# of local guests * 90%) = total # estimated to attend. 2  It’s a good idea to make an A list and a B list. 3  Send your a list invitations out 8 weeks in advance. 4  As you start to get acceptances and declines, you can start inviting some of the people from your B list.