Generally speaking, mine are in between 14.1 and15hh.
You can base your horse's future heights by the length of their cannon bones. The longer the cannon bone, the taller the horse, and vice versa for the other way around.
The cannon bone is the same length from when a foal is born to when they mature, which is why people use it to judge heights.
However, they are a lot of factors which can affect a horse's growth rate, such as nutrition and training.