So, I became really surprised when I noticed how much taller one of my mares got than I had ever expected her to. She’s Gawne is 16.3h and her projected height range is 15.1h to 16.1h. So now I’m curious as to how common it is for a horse to be taller/shorter than their projected height range. Before, I thought that a horse would always be a height within their range, but now I see that’s not necessarily true!
Has anyone else noticed a horse fully grown and outside of their height range?
The projected height is just an average of the parents’ heights. There is an element of randomness to the foal’s actual height.
I have two leased horses that are an inch shorter than they are predicted to be
I own a horse who stopped growing at 14.3hh. Projected minimum was 15.1hh.
I’ve had a few under predicted height none over that I’ve. Noticed
Technically, average +/- 2 inches to get the range. 
Foals can get height (or lack thereof) from either parent. Also, premie foals will be a bit smaller than their genetics dictate.
So, it looks as though it’s more common for horses to turn out shorter rather than taller. Thanks for satisfying my curiosity, everyone! 