Invitation List vs. Guest List?

Is there any strategy involved in coming up with the initial guest list? We originally had 140 people on our first version of the guest list, but we trimmed it back to about 110.
But if they say that 20% will RSVP NO, then, I'll be under 100, but then I migt have to pay for anything below the minimum? I'm just unsure of what is the most sensible thing to do. Invite more or less?
I'm trying to figure out if it woud be smarter to have a list of 120 to start with, and try to make a 100 minimum, or trim back even further to a list of 100 and try to make an 80 minimum?

any advice? We are planning a Winter Wedding on a Sunday, under a tight budget, for what it's worth.

Personally, I am approaching it as if every guest I'm inviting will say yes - meaning I know that if all of my 231 people said yes, then I can afford it. You don't want to invite more than you can afford and then panic if less than 20% can't attend.

You might want to have a 'B list' - send your invitations out as early as you can to the number of people you are confident you could afford, and then when the no's come in, you can send out invitations to some others. Lots of people do this. Just my two cents anyway!

You should always think every guest is a yes, cause you don't wanna be surprised at the last min when people you invited who you thought would say no say yes.

We have an a and b list. The b list is people who we haven't really talked to in a long time and would ike to invite if we can but aren't a top priority (I know that sounds mean but its the truth)