Relative scales...

It might help to try to get a sticky that lays scales out.  I have a question about different basis of scales.

I know that 54mm is about  1/35 - 1/32 scale.

I also believe that it's either 25mm (or 24mm?)  that's about 1/72 - 1/76.  Well, I think, because I have also heard of 20mm being pretty close to 25mm.  I've also have heard of smaller - like 15mm.

So, I would like to know what the relative scales are.  And, what are they based one (like a 54mm figure is about scale for a 6 feet tall person?   Same with 120mm?)

Part of the reason I would like this, is that I'm thinking of building a small vigenette of a section of Hadrian's wall.  I want to include at least a few figures, and would like to represent the full height of the wall - I know it varies.  I've never worked with, or even seen 120mm in person.  I know it should be about 2.4 times bigger than 54mm.  I'd like to do some good detail on the figures, but keep the whole piece reasonable in size.  Plus, I also have to convert the scale of the figures to build the wall (if they are approximately 6 feet tall, I could use that to factor the wall's height.)

Of course, it would probably be good for me to pick up some Roman figures in various scales, at least 54mm and 120mm, to practice with since I haven't worked with 120mm before, and really have only done 1/35 scale plastic figures for WW2 and Modern infantry.  I think I might do that anyway.  But, it would still be nice to have something that shows the various milimetre sizes compared to the x/yz scales, and their appx. real-life person size.  I mean, do all 120mm scale figures stand at attention at the same height?  Historically, this wouldn't be accurate.  But, sure makes model building easier.

Thanks.

Cor