How to cut your wedding guest list without a fight

Arguing over names gets personal fast. Arguing over a rule doesn't. So agree on the rules before anyone opens the list.
Start with the number
Your venue's capacity and your budget set the limit. Divide what you can spend on food and drink by the price per head, and check it against the room. That number decides the list.
Write everyone down, then split them
Put every name in three columns:
- Must be there: you'd move the date if they couldn't come.
- Want there: you'd be really happy to see them.
- Feel we should: you're inviting them out of duty.
Start cutting from the third column.
Use rules that apply to everyone
These are easier to explain than a single name:
- No colleagues unless you see them outside work.
- Plus-ones only for long-term partners.
- Adults only, or immediate family's children only.
- Haven't spoken in two years? Not on the list.
When someone asks, you can say “we kept it to close family” and mean it.
Decide about parents' guests early
If parents are paying for part of the day, they may expect to invite people. Give each side a number at the start. It's a much easier talk than removing names later.
Keep a short backup list
Some people will decline. Keep a B list in order, and send those invitations early enough that nobody feels like a last-minute addition.