What are the differences in viola sizes? Are they like the violin sizes - for kids and whatnot?
I deeeeesperately want a viola... i'm not going to get one just for the fact that i only started violin 6 months ago and i really need to stop buying so many instruments... i could afford one.......... but no i need to stop the 'i want to play that, lets learn it!' thing
But if i was to....(which im not. yet.)..... what size?

It depends entirely on your physical make-up - the only real way to find out is to hold a lot of them and see if they fit. You should be able to put it on your shoulder and put your left arm out, grab the scroll and hold it in your fingers with a slight bend in your arm.

Go to a music shop and try it out! Fun afternoon if you want a viola. Which you don't. Yet.

With emphasis on the yet.

A lot of primary school kids who play the viola actually use violins fitted with viola strings. Very confusing when they hand you what you think is a violin to tune but the strings just don't sound right.

Isn't the length of your fingers also relevant? I got a 17 inch viola because my arms are very long, but my little finger is quite short and I think I may have to downsize.

If you can hold the scroll in your fingers, you should be ok, but you're right that scale length comes into play (rather than finger length - you can get shorter scale lengths on longer instruments if that makes sense) - I made exactly the same mistake as you - had a 17 inch, struggled like mad to get my fourth finger in tune, then gave up and bought a 16,5 inch and the problem disappeared!

Best thing all round is to have a luthier look at you when you're trying them out, I reckon.

No they're not. It all goes on the back length. Back length 14 inches is the same size as a full size violin, and it gets bigger from there.

Liz

Aah i see.
So i could string my old violin as a viola and i'd have a 14 inch viola?

No, you'd have a violin strung as a viola (but of course there's no reason why you shouldn't do that if you want to experiment). There are differences between a 14 inch viola and a violin, but the differences are not always obvious. With the brand we are best known for, the only difference is in the depth of the ribs.

Liz