How many hours of sleep do i need for a university student of age 19 who goes to school for 15h, works 13h a week, and 30h of studying?

8 hours: Most people benefit from getting 8 hrs of sleep each night. Sticking to a set agenda each day should help make this possible. Also, have a regular routine before laying down at night will also be helpful in falling asleep and maximizing the sleep. I hope this helps.

8-9 hours a day: While there is some variation for each person, for your age, you should strive to get about 8-9 hours of sleep a night. Chronic sleep deprivation can impair your scholastic performance, a week has 168 hours. You have commitments for 58 hours, leaving 110 hours. Your sleep need is no more than 56 hours (9 hours * 7 days). You have adequate time to get the sleep you need.