pot size for 3

I'm looking for a pot for 3 people, just for boiling water for FB meals. The max I would boil at one time is 4.5 cups, which equals 1.125 L. I figured I can use a 1.3 L pot for this. But I see various posts that refer to a 1.3L pot as being OK for two people. I'm wondering why not for three also? Am I miscalculating or what ? Thanks, Barbara