Soprano

Soprano - aka Standard
This is a scale length of between 305mm (12in) to 355mm (14in) and these days usually come in about 340mm (13½in).

This is the original scale length for a Ukulele though in the past the average length was probably closer to 330mm, (13in). Some purists say that only Ukuleles of this scale length should be called Ukulele with the other scale lengths having related but different names like a big Mandolin being called a Mandola or a big Violin, the Viola. The difference here though is the step change in scale lengths, (the larger instruments would be more analogous to a Tenor Ukulele with no intermediate size), and the fact that the bigger instruments are also tuned differently to their smaller versions, (There are some people who suggest that Ukuleles of Tenor scale length should be tuned lower than the standard g~C~E~A, as well as the original tuning recommendations for Sopranos being a~D~F#~B. In practice though, what has happened is that all sizes of Ukulele, except Baritone, converged on the C tuning).

This size came from that of one of the Ukulele precursor instrument, the Braguinha, and its forebears, the Cavaquinho, (with the tuning coming from another, larger 5 stringed Portuguese folk instrument the Rajão), and of course the Cavaquinho can be traced back through a number of Portuguese and Iberian iterations before eventually going back to a simple Lute somewhere in the dim and distant past. This heritage also gave the Ukulele its traditional figure 8 shape as it has often been asked why, given the size of the instrument, does it need a waist? Its understandable in a much larger instrument like a Guitar when you sit to play it, but not needed in a Ukulele, (as demonstrated by the Pineapple Ukuleles). Well it is only tradition, I assume the 3 original makers didn't want to change what they had learned when making Braguinhas in Madera, and this is what they taught the next generation of Hawaiian luthiers so by the time Sam Kamaka came up the the Pineapple, The Ukulele already had 30 odd years of being figure 8.

The tuning for a Soprano can be either C, (g~C~E~A), or D, (a~D~F#~B) tuning. Neither is particularly "right" and it is often the case to have two Ukuleles and use both. The C tuning has become more popular over the years because it allows for songs in the keys of C, D and G to be played using the easy chord shapes, whereas the D tuning only D and E are easy to play (and a lot of songs are written in the keys of C and G). You can always change the tuning appropriately to play in a different key, but be careful how high you go or the strings may break! Alternatively you can transpose, (but then you end up with a lot of songs sounding very similar). Yes you can use a capo too, but me and George Formby both go with having a Ukulele tuned each way, (and it gives an excuse for having more than one Ukulele!)