It really doesn't matter at all for now. But you should know the average which is about 5 inches. The thing is that some (a lot) of males gets to puberty
but don't see any changes. This is because it will develop later (even later than 18 years of age) because it changes from one person to another. So don't worry if it hasn't grown yet but if it hasn't for another year or something, I would visit the doctor (even now will be fine).