Novice Question on Pot Odds

[kalooki45]

Thanks to all the great folks out there who share their wisdom with us newbies!
I'm wondering about pot odds--I was trying to make a chart that would list # of outs and then put the even money odds for different stake games beside them. (sort of a cheat sheet)
Here's what's got me--do you calculate the odds based only on the smallest unit bet? Say in a 1/2 game--if 3 outs is about 15:1, then you'd need $15.00 in the pot to make it even money?
OR is it by dividing the AMOUNT you're putting in (or about to) into the amount already in the pot?
Or have I missed the boat completely??
Thank you! [img]/images/graemlins/heart.gif[/img]