Khan Academy - http://www.khanacademy.org/ - is often cited as a great online resource for learning mathematics and other subjects. I have heard many good things about this website and was wondering in what depth are subjects covered?

I know Khan covers topics in (highschool) algebra and calculus. What other subjects are treated? and at what level? How rigorous is his treatment?

Some background: I teach at a university and would like to know if this is a good resource to point students to. I'm thinking primarily of students who are having trouble in college algebra, calculus I, etc. Not necessarily math majors.

To be crystal clear: I'm not looking for suggestions regarding other online resources. I just want an honest critique of Khan Academy from those who've explored what it has to offer.

Bill Cook
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    Khan (from south Asia) not Kahn (central Europe). – Henry Nov 08 '11 at 14:52
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    Accessibility, and breadth. For many people without access to a college education (say, because they're working), and who find the video format better than books, it's a way to get reasonably decent lectures on many many topics (he even teaches history and biology now), which is great. – ShreevatsaR Nov 08 '11 at 14:58
  • @Henry Oops! :) – Bill Cook Nov 08 '11 at 15:09
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    Regarding the math, some students like it because it doesn't sound authoritative and provides certain type of hand-holding for every level. That is something research level mathematicians have hard time to understand for their own reasons. –  Nov 08 '11 at 15:31
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    Another point: it appears that the videos are split into small chunks, with each video having one main point and being short enough to sustain the attention of the average viewer. So even those whose attention spans have withered away (again, say, because they are no longer in a classroom setting) can get something useful out of these videos. In fact, one could say that the traditional long-form lecture fails such students, and Khan Academy videos fill that gap. – ShreevatsaR Nov 08 '11 at 16:58
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    I think the answer to your question is to tell your students about it some semester and ask them what they thought of it. None of the people giving comments or answering are in the position of the students. But, I would like to say that it doesn't matter if it is missing a bit of rigor or depth or whatever. They're going to your class. They're getting that stuff. This is a supplement. If it helps them understand several things better, that's good. – GeoffDS Nov 08 '11 at 17:38
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    A critique of the videos which, IMO, makes an important point of what's wrong with them: [Khan Academy and the Effectiveness of Science Videos](http://www.youtube.com/watch?v=eVtCO84MDj8). I personally haven't watched enough of them to really be entitled of giving a judgement, but from what I have seen I strongly disapprove of the lack of _motivation_ why stuff is done the way he explains it. That may be just fine for a student who's not interested in actually understanding anything but simply wants to pass some exam, but they will probably gain little benefit from this in the long run. – leftaroundabout Nov 08 '11 at 19:28
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    There is a vote to close the question as not constructive. It will be great if the voter please explain the vote. Has it got anything to do with the question being soft? – Srivatsan Nov 09 '11 at 04:22
  • I used Khan Academy while learning pre-calculus and a bit of single variable calculus. It helped me a lot, and I do recomend it for who is beginning. It is quite informal, though. At some point it became just too weak for me, and then I went for MIT OCW's videos. – Ivo Terek Jan 05 '15 at 00:07

6 Answers6


I find that the impressiveness of a Khan Academy video for me is negatively related to how much I know of the subject. As a math graduate student and calculus teacher, I find Khan's math/calculus videos the least impressive of the lot, his physics/chemistry/biology videos mildly impressive, and his history videos the most impressive.

What this suggests to me is that the Khan Academy is lacking in depth and clarity of presentation, as well as in addressing the subtleties and key issues that would be necessary to impress a person with some knowledge of the subject. Watching the Khan Academy is roughly akin to having a smart kid in your class (who is learning the subject along with you) explain to you what he/she has understood of the subject. It is not really comparable to how an expert teacher would convey the material.

This may not be completely a minus, because the lack of polish and the chumminess of the videos might itself be an endearing factor that makes people more comfortable with the videos. It also makes it easier to scale up and make a larger quantity of videos. Also, the low intensity of the videos makes it easy for a person to watch them when tired and distracted without missing out on too much.

Here are some examples of sloppiness:

(i) In the calculus videos, when I viewed them, the graphs were drawn very shakily, extremely hard to understand, and not well labeled. (ii) In a video on classical mechanics, there were some inaccurate statements about normal force, describing it as a reaction to gravitational force in the action-reaction sense (this was fixed later, I think). These weren't merely careless errors in speaking, but reflected a deeper lack of understanding. (iii) The examples and symbol choices are often confusing.

If you are recommending watching Khan Academy videos, I suggest you add the caveat that they should not expect a lot more (in terms of accuracy and quality of explanation) than they would expect learning from their colleagues.

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    > *"Also, the low intensity of the videos makes it easy for a person to watch them when tired and distracted without missing out on too much."* I think this is an important point. It means that the average multiply-distracted internet users of today can get something useful out of the videos, which they may not be able to get from books or longer-format videos. – ShreevatsaR Nov 08 '11 at 17:01
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    Shreevatsa, not sure you're right. If a user remembers 40% of Khan's video, and 20% of another video that is thrice as dense, the arithmetic supports the denser video. It's unclear how the trade-off works in practice, it could go either way. – Vipul Nov 08 '11 at 18:29
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    I agree, but besides %, another point is viewers feeling they've learnt something (and thus being motivated to continue watching more videos). If someone watching a longer video in their normal internet-distracted way realises they're not following much (or gets bored), they may just give up, while if they somehow complete watching a Khan video they may feel they've actually learnt something or passed a milestone, and continue with another small Khan nugget video at some later time. Of course, this is all speculation: some students are more patient and even Khan length is too much for some. :) – ShreevatsaR Nov 12 '11 at 16:13
  • `roughly akin to having a smart kid in your class (who is learning the subject along with you) explain to you what he/she has understood of the subject`. Perhaps unfair; more a graduate. But it conveys both the lack of depth and the advantage of someone who is closer to being your peer explain it. At uni, the tutors would often be better at helping students than the lecturer, because they'd been a beginner more recently. – hyperpallium May 20 '18 at 06:56

I like the videos.

But I don't think they are what is special about khanacademy: instead it is the combination of the self-study videos together with the machine-graded and assisted exercises, where a human tutor can monitor progress on the exercises. In a sense this might be seen as the reverse of traditional education where the tutor teaches and the student does exercises alone. Time will tell whether it is a better model.

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I've looked around khanacademy a bit and I'm not really impressed. There's certainly nothing wrong with it, but it gets too much hype. There are math tutors on youtube (look up PatrickJMT) who do a better job.

Brendan Cordy
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    What are you not impressed with? Depth? Rigor? Explanation? Number or quality of exercises? – Srivatsan Nov 08 '11 at 15:08
  • Just the clarity of presentation in the videos. I admit I only looked around a little, and this was a while ago. I'm not saying it's not a good resource, it certainly is. I just feel like it gets too much hype. Youtube is full of great math tutors, MIT's opencourseware videos, etc. – Brendan Cordy Nov 08 '11 at 15:46
  • After reading Henry's post, I realize I may have missed the point though. I didn't know there was any student-tutor interaction going on through the website, so I can't comment on that. – Brendan Cordy Nov 08 '11 at 15:51

Apart from algebra, some calculus and basic maths the site also covers Geometry and Trigonometry, the 2 subjects that I'm using Khan Academy for at the moment.

The tutorials aren't very rigorous, but that is a positive thing for students who find calculus challenging and are not math majors (that described me by the way).

Although my first ever proof was actually from this site, it dealt with how to prove the angles in a triangle always add up to 180 degrees. It was pretty cool.

I actually think this site really is most ideal for people who need to brush up on their basic math skills before/while taking a first course in calculus.

I also get bored with my head stuck in a book all the time, and it's nice to watch a video once in a while. And finally, the many online exercises keep me from nodding off, and if you are somewhat immature you can take pleasure in collecting badges and energy points, as I do! ;)

Tim H UK
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I've used Khan Academy videos from time to time, and my biggest complaint would be the lack of professional oversight. For example, in his video about the sodium-potassium pump he is just wrong about how the membrane potential is generated, and how the action potential is transmitted. In this case, there is a correction video posted, but I remember there were some other videos with smaller mistakes that were only pointed out in the comments, or not at all.

That said, I still think it's an excellent learning resource, because the short videos are easier to watch than reading the same content in a book, and Khan is very good at explaining things.

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    I think it's weird that he's the only one doing videos. If he could get more funding, which he probably can and does, he should hire experts to do videos. Or, they could volunteer. He could pick people known to be good teachers as well. – GeoffDS Nov 08 '11 at 17:36

I use Khan Academy extensively with my own children and (together with friends) to help kids in Newark, NJ. Khan is much different in practice than what it looks like on the surface.

Khan has lots of bite-sized video lessons that are well-produced (even when you only see a simple blackboard). They range in quality from pretty good (most of the math) to excellent (browsed through some amazing musical theory and social science videos). Khan is judged on the videos, but they're almost besides the point.

Computer-based education is only clearly superior in mathematics only (so far). This is because computers are far better-suited than teachers or books to:

  1. Move at your pace
  2. Allow guessing before learning to prime you for what's coming
  3. Provide time-spaced learning to ensure knowledge sinks in
  4. Check for mastery before allowing you to move forward
  5. Motivate via gamification
  6. Probe previously-mastered areas for weaknesses
  7. Help coaches to check for appropriate progress

The videos, while very helpful, are only a last resort. You should only watch the video after first guessing and then using the written hints.

Khan is amazing in the areas covered by exercises. Khan is far less effective in subjects with videos but no exercises (higher areas of linear algebra, calc, etc.). I expect Khan to gradually expand their coverage and it already seems like a superior alternative for non-math/engineering majors.

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