If you pull out your hair, will it grow back? if so how long will it take?

You may ruin it: Usually it grows back eventually, but some folks pull it compulsively and this can end up spoiling the look of your scalp for life. If you're asking because you're a compulsive hair-puller (i suspect this is largely genetic though some psychiatrists can treat it), a great strategy for a man is to buzz his hair with clippers daily "like the other super-tough guys".