If I don’t sleep at least 8 hours I am useless. Admittedly I get less during the week when I’m sticking to my study routine, but I make up for it on Saturdays as possible.
I used to sleep very little in high school, roughly 5 or 6 hours a night. Whenever I changed to 8/9 a night, it was like pouring gasoline on a flame in terms of the impact on my focus and such. I don’t have a specific amount of time I sleep but averages between 7-9 a night, as I rarely use the alarm clock. If I’m relying on an alarm clock, I realize I’m getting too little sleep and adjust my schedule.