It's known in the wedding industry that not every single person you invite will show up.
However, what percent of guests should you expect?
According to a study by TheKnot 10 to 20 percent will decline the invite.
However, ten percent of those who said they'll come don't end up showing up.
If you invite 200 guests, 20-40 will decline the invite, leaving you with 160 guests, then around 16 of them who said they were coming will end up not showing up, leaving you with 146 guests.
Now, some weddings have all the guests who said they're coming show up and some have even less.
A word for the wise: Never assume people won't show up, always have enough for the number of RSVPs +5, this will avoid any issues.