realistically, how many hours of studying do you need to guaranteed pass a STEM class

[kathisterima]

realistically, how many hours of studying do you need to guaranteed pass a STEM class? For example, you have X h of lectures per week on this class, which sums to Y h of lectures throughout the semester. Do you need to be putting all those hours of studying into that class in order to pass it? Btw, I know some classes are very demanding and need you to do homework projects alongside the lectures, lets talk about them as a different case

It depends on the class, but for a typical STEM course that mainly consists of lectures, exams, and some problem sets, you don’t necessarily need to match lecture hours 1:1 with studying. However, there’s a general rule of thumb:
For every 1 hour of lecture, expect to study for 2–3 hours outside of class.
So, if you have X hours of lecture per week, you’d typically need:

• 2X to 3X hours of self-study per week.
  
• Over a 15-week semester, that’s 30X to 45X total hours of studying.
  

What’s the “Guaranteed Pass” Level?

• If you’re aiming just to pass (like a C or low B), you might get away with 1X to 1.5X hours per week of studying.
  
• If you want a solid A or B, you probably need 2X to 3X hours.
  
• If you’re naturally strong in the subject, you can sometimes get by with less, but it depends on the class and your background.
  

Case 2: Heavy-Duty STEM Classes (Projects, Labs, Homework, etc.)
These require way more time because problem-solving, coding, and lab reports eat up hours:

• Engineering, Computer Science, Physics, and Math-heavy courses often require 4X+ hours per week beyond lectures.
  
• If there are projects, expect to dedicate entire weekends before deadlines.
  

So, Do You Need to Match Lecture Hours?
Not necessarily! If you actively pay attention in lecture and take good notes, your study time can be more efficient. But if the class is super hard and you struggle with the material, you might need to put in as much or more study time than lecture hours.
Are you thinking about a specific class?

In the case you have 25 subjects to pass, and say about 10 of them are heavy duty: You have 4 months to prepare and you are given a 4 week exam period, where you cannot prepare but only revise your homework. Would that be doable? Do the math.

Alright, let’s break it down mathematically and see if this is even feasible.
Given:

• Total subjects: 25
  • Heavy-duty subjects: 10
    
  • Regular subjects: 15
    
• Total time for preparation: 4 months (~16 weeks)
  
• Exam period: 4 weeks (only revision allowed, no new studying)
  
• Actual study period available: 12 weeks
  
• Assumed lecture time per subject per week: Let’s estimate 3-4 hours per subject per week
  

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Study Time Required Per Week
Using the standard rule:

• Regular subjects (~2X study time per lecture hour):
  • If each has 3 hours of lectures, that’s 6 hours of studying per subject per week
    
  • Total for 15 subjects: 15 × 6 = 90 hours per week
    
• Heavy-duty subjects (~4X study time per lecture hour due to homework/projects):
  • If each has 3-4 hours of lectures, that’s 12-16 hours of studying per subject per week
    
  • Total for 10 subjects: 10 × 14 = 140 hours per week (assuming 14 hours per subject on average)
    
• Total weekly study time required:
  • 90 + 140 = 230 hours per week
    

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Reality Check: Feasible?

• There are 168 hours in a week.
  
• If you sleep 7 hours per night, that leaves 119 waking hours per week.
  
• If you dedicate every waking hour to studying, you still fall 110 hours short every week.
  
• Even if you pull insane 16-hour study days every single day, you only get 112 hours per week, which is still 118 hours short weekly.
  

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Conclusion: Impossible Without Adjustments
The math says this is not humanly possible under normal conditions. You’d have to:

1. Prioritize: Drop or delay some subjects.
   
2. Compress: Focus only on high-yield topics instead of trying to cover everything.
   
3. Leverage previous knowledge: If you’re strong in some subjects, reduce their study time.
   
4. Use shortcuts: Study from past exams, summaries, and problem sets.
   

Final Verdict
Unless you’re a robot, you cannot study 230 hours per week in a 168-hour week. You’d need to strategically cut study hours, rely on past knowledge, and optimize your learning.

in the scenario of someone being familiar with the topic, and having been in lectures, although long time ago, to the point his familiarity isn't useful if he was given an exam paper to answer right away. Would that be doable?

Now this is a more reasonable scenario. If the person has prior exposure but isn’t exam-ready, they have a big advantage: they don’t need to learn from scratch, just re-learn and refresh.
Adjusting the Study Load for Someone Familiar with the Material

    Instead of needing 2X to 4X study hours per lecture hour, they might get away with 0.5X to 1.5X study hours per lecture hour.
    This means the study load is significantly reduced.

Revised Study Time Estimation
Regular subjects (15 subjects)

    Instead of 6 hours per week per subject, they might need 3-4 hours per subject per week.
    Total: 15 × 4 = 60 hours per week

Heavy-duty subjects (10 subjects)

    Instead of 14 hours per subject per week, they might need 6-8 hours per subject per week.
    Total: 10 × 8 = 80 hours per week

New Total Weekly Study Time

    60 + 80 = 140 hours per week

Is This Doable?

    You have 168 total hours per week.
    If you sleep 7 hours per night, you have 119 usable hours per week.
    If you study 14 hours per day, you get 98 hours per week, which is 42 hours short.

What Needs to Change?

    Increase efficiency – Focus on high-yield materials, past exams, and condensed notes.
    Reduce study hours per subject further – Prioritize based on difficulty.
    Use active recall & spaced repetition – Instead of passive rereading, test yourself constantly.
    Sacrifice some rest/free time – Maybe stretch to 16-hour study days a few times a week.