What is the IQ of Sherlock Holmes?
Radford estimates Holmes' IQ at 190, which places him much, much higher than our crazy-haired scientist. Since then, there have been many more studies on this fictional character leading people to lower his intelligence rating, but he still remains one of the smartest characters ever written.
His weakness in this respect is that he constantly desires to prove to people how clever he is, as though he believes his only value is in his brain and intelligence, his constant need to show off reveals something of a boastful ego that can easily be turned against him, particularly when he underestimates his opponent …
Sherlock Holmes, in all his brilliance, is a strange man. It's obvious that he's a man of great intellect, yet he's utterly ignorant about certain subjects. It's said that he doesn't even know the earth revolves around the sun.
The exact IQ is obviously unknown but since John is a doctor and people who receive a Ph. D are known to have an average IQ of 120-125, I would estimate John Watson's to be around there as well, which would place him roughly in the 90-95th percentile.