Hey all. So I have never been good with math! So please bear with me.

I am looking at an '83 Peugeot CPX-99 frame (has everything but wheels and tires and chain). It is 20", by the owner's description. So what does that mean for me? I am a 5'7" man, so I have found a LOT of good deals that are just too big for me. My inseam is 28", so I need a bike that is 28" to the top frame bar.

So, since I would be building this one up (my first), I would have to account for the sizing myself, correct? Or does a frame determine the rest of the measurements? I figured I could put tires/wheels on that would make it a 28" bike. So... What's that? A 16" wheel? Haha.

I don't know. Could someone help? Can't find anything on Google.