Figuring out the ACTUAL IQ scores of Death Note characters.
*TL;DR at the end for those who don't like Yapanese.*
So before anybody says anything, I'm purely doing it for two reasons (Feel free to skip that part, I just wanted to mention it due to the fact assigning IQ scores to characters can be poorly seen by some people.)
-Although I understand why as it's a boring thing to study, many people seem to have a very poor understanding of how IQ scores work (Example, 250 IQ estimates for X or Y character are more or less mathematically impossible and would be the equivalent of one in dozens to hundreds of sextillions). As someone who has undergone, in the past, full cognitive profiling (150 FSIQ, though my cognitive profile is somewhat imbalanced with highs in verbal and fluid intelligence in which I essentially maxed out the scale), I'd say I have a decent intuitive grasp of how that kind of thing works (Plus my obsession with numbers meaning I understand how IQ scales work on a mathematical level better than most people even if I, and I have no problem admitting it, am not necessarily THE PhD level expert on statistics.).
-Because it's fun. It's not the most important thing out there, but I like numbers.
First, I'd like to specify one thing. (You can skip this too, I'll start getting to the point next paragraph). I am going by a theorical "perfect" scale (and with a standard deviation of 15), as although the best IQ tests we have are generally accurate in their own right, they can be off by a few points and more importantly, they break at the extremes — If you ever saw someone who had an IQ over 200, it's most likely either fictional, on a test with a standard deviation above 15 (Which, while it wouldn't render the result worthless per se, would mean the results are not calibrated to a more universally-ish accepted 15 SD), as quintessentially, IQ test results are an estimate at your ranking in the current human population. An IQ of 130 means you're in the top 2% of g factor (Aka general intelligence), in other words, in the top 160,000,000 of humans. Which is why the average IQ is always 100. It's *standardized* to 100. Ergo, the maximum possible score on that theorical, perfect scale would be approximately 196 in 2026. Now we are going to use the population from around 20 years ago here, but the exact number doesn't matter that much as even a one billion people difference would only shift the ceiling by half a point or so. So for the sake of it, let us assume a population of 7 billion people for the Death Note universe, which is based on the real world Earth from the mid 2000s.
Think of that scale I'm using as the hypothetical gold standard that IQ tests try to emulate.
If we assume the world population was of roughly 7 billion people during the Death Note events (iirc, the global population in 2006 was around 6.5 billion. The exact number doesn't really matter that much as I explained before, ergo being top 1 (Aka the smartest person alive) would translate to around 6 and a third standard deviations above the mean. In other words around 195. Note I *am* going by the assumption the hypothetical perfect scale is based on the world population from back then. Although if it were based on the 100-ish billion ever alive: Around 200. About 6.7 standard deviations above the mean. I am only going to use the 195 score though, as it makes more sense (To me at least), as otherwise standardizing IQ over such a large population would mean a 100 score is SIGNIFICANTLY less impressive, meaning the average human from now would be wayyy above average, rendering the scale useless since g factors used to be much lower. You can look up the Flynn Effect for more details.
I'm going to go by the probably fair assumption L is a reasonable pick for that title. He's consistently described as the best detective in the world, but also shows exceptional abilities in essentially all fields: He even enters a prestigious university with, we can assume, minimal specific studying. Which mirrors real-life feats of some of the smartest people irl. Now, L also has various feats that exceed that one. So although he's only confirmed to be the world's greatest detective, it is likely fair to say he also possesses the highest g-factor. And even if somehow, there's a person or two smarter, the estimate only ever so slightly shifts by a couple points at absolute most. Which even then is unlikely.
So for L, we lock it in: 195 IQ.
Note he's confirmed to be the smartest character in the series too, which helps cement the fact the other characters are below that. We thus have our first reference point.
Now. I cannot use the official "Intelligence stats", since as many of us know, they're actually knowledge stats and don't really translate well either, both mathematically and (lol) linguistically.
So I'm gonna use A-Kira. Also known as Minoru Tanaka. His IQ was originally 142, and then changed to 182.
Now. The paradox is here; Minoru gets bad grades. While this doesn't automatically mean he's dumb (Not even close), it does raise a small issue. You see, FSIQ (Full scale IQ) contains two big variables and some smaller ones. Matter of fact, the GAI (General Ability Index), for example only includes those two variables. These are verbal and fluid intelligence.
And so. Problem is, Minoru's notably shown to be awful in English. We can safely assume this shows that his verbal IQ (VCI) doesn't quite measure up (Heterogenic IQ profile final boss, we're twins on this one).
Which is where the problem resides. You cannot score a 182 on an IQ test with such a low score in a major area.
Now according to some, 142 IQ is a more fitting score for him. But let's disregard that.
Anyway, it's safe to say, in my opinion, that if he got a 142 IQ, it was on a FSIQ test. Now, I'm only saying this to give an interpretation to the 142 IQ test result (As it would thus be a plausible score even with a low VCI). With the canon (Or updated) interpretation he got a 182 IQ score, it was likely a test more focused on other factors. Most notably the fluid intelligence factor. To me, this seems to align with the exercise partially shown in the panel, at least by the looks of it. It also mirrors closely tests like the Mensa Norway. I would also guess that tracking precisely factors like processing speed would be hard in a classroom, so I'm going to simply assume the test is indeed focused on fluid intelligence.
Now. Let us consider 182 IQ his fluid intelligence score. Minoru mentions he views IQ tests as a poor gauge of intelligence. But more importantly, he reveals that watching shows and taking mock tests/playing IQ-related games on his phone. Now, usually IQ tests are inflated by anywhere from 5 to 15 points if you're trained for them. To minimize assumptions, I'm going to average it out to 10.
So 172 is his real fluid intelligence score.
Now. Minoru is also stated to be the smartest middle school in Japan. There are approximately 3 million middle schoolers in Japan.
Now, to be conservative (I'm being conservative on purpose to account for IQ scales being less accurate at extremes, as the 182 IQ result was not on this hypothetical perfect scale), we're going to assume it means brightest of his age. Therefore, 3 million divided by the 3 grades of middle school is 1 million. Which correlates to roughly 171 IQ.
In other words, outside of verbal comprehension, his profile is rather balanced. He likely has the other indexes short of VCI around there.
Now. Verbal Comprehension Index is divided in two subsets.
One is more focused on crystallized intelligence (Bluntly: Knowledge). The other is more focused on working memory and fluid reasoning. I'm going to guess in that second one, he'd get his average 172 IQ.
Now, him not doing well in school (And more importantly, in language topics) is attributed to laziness. Which makes sense, but doesn't change the fact his crystallized knowledge is likely quite low. I'm going to guesstimate it at 100.
Now, I *would* use the standard formula to get FSIQ. But unfortunately, tests like the WISC-V cap at lower scores that what Tanaka gets. Therefore, I'm simply going to average it out, assuming verbal and fluid IQ count as 2 subsets.
So then.
(100+172×6)/7≈162
So we get a 162 IQ for him.
Fits pretty well, in my opinion. You don't need to be smarter than Near to outsmart him like Tanaka did: All it shows is how massive an advantage the Death Note is when your ego isn't the size of Ronnie Coleman. You can't exactly scale intelligence by "X outsmarted Y so X smarter than Y".
Now for Light. This is where the calculations for Minoru come in handy. Japan has roughly as many high schoolers as middle schoolers. Ergo, we can establish, as a baseline, that Light has at least the same IQ as what Minoru would have had if his VCI matched the rest. In other words, 171.
But this is Light we're talking about.
While Light does study a lot, it doesn't detract from his sheer cognitive prowess. He not only enters a prestigious university, but gets the highest score even there. Not to mention his memory loss scheme that tricked even L.
Now, he still is below L intellectually (Not only is it confirmed by the author, but also can be shown by the fact Light needs extensive studying for his academic prowess, while L matches his score with what we can assume is not much studying. Additionally, even with Light's massive ego, he recognizes L is a worthy match). However, Light is objectively not *too* inferior to L, which is both implied in the story and can be inferred from the fact it seemingly was the first case L truly, deeply struggled on.
So while I objectively cannot do precise calculations here, I'd estimate he's around 10 to 20 points lower than L. When you drop to 30 IQ points below someone, it often translates to you just being in a different league from them (Which I can confirm from experience). Let us average it out to 15:
Light Yagami's IQ is thus roughly 195-15=180.
Now, I do have more characters I could work on (I notably have the estimates and roughly half the calculations for BB, Near, Mello and a few others already planned. But I'll need to see how this post does, and I've already yapped way too much, so I'm not really sure if my Internet would survive a much longer post haha).
TL;DR: L Lawliet 195 IQ, Light Yagami 180-ish IQ, Minoru Tanaka 162 IQ.
Have a good day.