(I posted this in another thread; however, I’m reposting since I see this is a more appropriate thread for it and hopefully it will help others.)
My wrist size is 14 cm and although I fit both 15 cm and 16 cm, I went with 16 (using the Cartier wrist sizer really helps in deciding!).
Quite honestly, I believe VERY, VERY few people actually end up purchasing a size 15 cm bracelet (even if you are very, very petite and small like I am), and usually those who fit both, should probably go with a size 16.
I’ve even read a few incidences where people with a wrist of 13.5 cm, which is tiny, regretting size 15 when the general rule of thumb is adding 1.5 cm for the perfect fit).
I am able to turn the size 16 easily on my wrist (from all areas: wrist to where it lands); however, it doesn’t turn on its own. I don’t think there’s anything wrong with being able to turn it manually on one’s arm so long as the bracelet is not doing it own it’s own from just normal wear - in which case, it’s probably too big.
From all my research & everything I have read (and I have READ A LOT!!) the bottom line is generally (MORE LIKELY THAN NOT) most people will end up purchasing size 16 and in extremely RARE cases (a very miNUTE percentage of people) end up with size 15 and are happy with it.
Therefore, if in doubt, go for size 16!! Chances are it’s probably a better fit in the long run!