How much can hair grow ?

If the average person loses 100 hairs per day, how come we don't become bald. If we lose that amount a day, that can add up to 100,000 within several months. Also i'm trying to grow my hair like Zac Efron and haven't trimmed my hair in 2 months. How much hair can i grow in 4 months ? I don't smoke / drink, have a healthy protein diet since i work put & don't use blowers / straighteners... What do you think ?