My height is 172 , i'm turning to 18 in a couple of months, how much are the predicted cm i'll gain till 21 and how can i try to boost the cms to grow?

No growth last year?: If no growth in the last year, then growth has finished. Most people reach their maximum height in their late teens. Without nutritional problems or chronic childhood illnesses, height is largely based on genetics and parental heights. Aside from eating right, exercising, sleeping well, and being happy, there's not much a person nor his doctor can do to increase height.