My 3 yr old national show horse (3/4 arab 1/4 saddlebred) is currently 15.2. Arabs mature slower so do you think he could possibley make 16 hands when he matures? My trainer thinks he probably will. His parents were around that height ( not sure the exact height of them but I remember my trainer mentioning that they were taller lol). Im hopeing he will get a bit taller so when he is older he will be able to handle higher jumps lol
Breed is not a significant factor regarding when a horse will stop growing. All or most horse's bones will stop growing at age 5-6, so your horse will not grow any taller after that (although he will 'fill out' with age and training for the rest of his life). However, most of the height growth is done by 3-4 so I doubt he is going to get much taller. I would say his adult height is going to be a generous 15.3, but it would help to know the exact heights of the sire and dam. Also, height isn't everything when it comes to jumping. There are many famous jumping horses who are in the 15 hand range that could jump much higher than a typical 16.3 horse.