Basic size question

In searching for answers to my question, I found this forum. So here goes.

I use Courier 12-point. And if I print something out three times–once in TextEdit, once from Google Docs, and once from Pages, I get three different sizes of text. So what I’d like to know is, #1: Why? and #2: Is there a reference I can go to, or can anyone tell me, which of these is most accurate?

Also, I’ve noticed that if I print in TextEdit, and then stretch the window across the screen, even though the font size still says “12” on each, the stretched screen will end up printing at a much smaller font.

This is driving me bonkers.

-Danny

If the font used is Courier New 12 point, then the way to tell which printout is most accurate is to measure it.

Ten characters should be exactly 1" and ten lines of single-spaced text should be exactly 136 points, or 1.89"