Answered on Quora.
It’s very important, but as the answers below suggest, no school will ask you for that, and you might not even want to volunteer it. Some of the answers below don’t make sense.
Some say IQ doesn’t matter, grades do. IQ is very highly correlated with grades. Testing well on GRE’s will be very highly correlated with IQ. Of course the ability to do good research will be well correlated with IQ. And I am sure that recommendation letters and their quality is correlated with IQ also.
So most of these answers are circular, tautological. They are saying, “IQ isn’t important. It’s all these other things (that just happen to be highly correlated with IQ) that are important.” So IQ’s important after all.
Some quotes are correct though. You will have to work your ass off in grad school no matter what your IQ is, and you may not even graduate out. I almost didn’t get my Masters, and I have a stratospheric IQ. Everyone wants to get the doctorate, but the Masters was such murder that no way am I going for something a lot worse.
IQ is natural intelligence.
One answer below says they are looking for grad students who can come up with novel methods to solve unsolved problems. What do you think an IQ test looks for almost more than anything else? Just that.
Bottom line: If you are thinking of getting into grad school for purposes of getting a PhD, an IQ of 125 is highly recommended: this is the average IQ of PhD holders. I suspect there is a floor of ~115 for PhD degrees. There is a similar floor at that level for physicians.
Go ahead and look up your score from school or pay a clinician to administer a good test, or if you are still in school, ask to be tested. Go the Psychology Department and ask if the Counseling Office balks – they often will test you for free.
If you do not have at least a 115 IQ, I would seriously reconsider trying to get into a PhD program at a top university. You are setting yourself up for failure. The only exception would be if you have a very lopsided IQ such that say you have great math skills but poor language skills so you end up like the well-known female mathematician with a 98 IQ.
17% of the population has an IQ of 115+. That’s 54 million Americans, which is a lot of people.