how much do you sleep in a day???(means in 24 hour)

i usually sleep 7 to 8 hours a day. i think that's normal. but before, when i was in med school, i was only able to sleep 3 to 4 hours a day. i had a 7 to 7 schedule in school and arrive at around 9 to 10 pm. then, i have to study and do my homework. i have a very hectic schedule then. but now, i have less things to do. i am able to have more time to rest.

why you sleep only 5 to 6 hours in a day.a healthy person must take sleep 8 hours in a day and i also sleep atleast 7 to 8 hours in a day.