Plan a weekly study schedule around your classes and free time.
A weekly study schedule is best expressed in sessions rather than hours, because sessions are what you actually place in a calendar. Available hours divided by session length gives the weekly supply, and allocating it by weight rather than equally lets a difficult subject take a larger share without leaving the rest unplanned. Sessions per study day is the check on whether the plan fits a day.
Session supply
Weekly sessions = floor(weekly study hours x 60 / session length)
Weighted allocation
Sessions per ordinary subject = weekly sessions / (subjects + extra weight); hardest subject gets that x (1 + extra weight)
No. Weight by difficulty, assessment weight and how far you are from your target grade. Equal allocation is simple but systematically underserves the subject that needs most work.
Three to four hour-long sessions is a full study day for most people alongside classes. Beyond that, quality falls faster than the added hours compensate.