From my reading, hair grows an average of 1/2 inch per month, 6 inches per year. Some folks faster, some slower.
There are things that will impede hair growth and benefit it, and it tends to be the same things that improve growth/health in general. Eat well. Rest well. Manage stress.
I've heard that consuming gelatin will help with hair and nail growth. I think that goes back to eating enough protein. Protein is a key component of hair, and if you don't eat enough (low protein diet), then that could impede natural, normal "your rate" hair optimal growth rate.
I know my thinning hair (menopause, hypothyroidism) got fuller when I changed my diet, adopted more nutrition (lots of fruits/veggies) and upped my protein intake. I can't take biotin--I break out--but I've seen some folks talk about its benefits to hair.
If you want to optimize growth--do the things that optimize health in general, eat good protein sources, and make sure you aren't missing any vital nutrients in your diet.
And if you don't have medical issues, look into hair growth supplements, like Ultra Nourishair or Biotin, etc. (Again, only if your doc is okay with it is my rule for strong supplements.)
I you skimp on nutrition, eat poorly, don't rest well, get overly stressed, don't do good health stuff, yeah, that can mess with your hair.
So...be patient...and take good healthy care of yourself.