Beware the courtesy invite! You know that distant relative you've never met, who lives in another country. Your co-workers at the job you just recently started. Your boss. Your friend from college who you don't talk to anymore. Your parents' friends. And then, that guest may bring a date!
If you invite them, be prepared for them to say Yes!
While 75% of the invited actually attend, you can not plan around that guess/hope - I've planned weddings where 50% rsvped Yes, and weddings with 100%! You just never know, so be prepared and plan for 100% just in case. Then, if you end-up having more than 75% attend, you can accommodate them in both your venue space and budget.