From 1981 to 1991, the LSAT was scored on a scale where 10 was the lowest possible score, and 48 was the highest. In the below chart, we see how various scores equated to percentile rank among those who took the LSAT (an elite sample):

LSAT scorepercentile among elite sample who takes the LSATSourceZ score assuming LSAT takers form a Gaussian distribution
3251year unspecified, note 79, Rothstein & Yoon 20080
3565Circa 1990 distribution+0.4
38791990- 1991 distribution; note 53
Rothstein & Yoon 2008
+0.8
41891990-1991 distribution; note 53 Rothstein & Yoon 2008+1.2
41901990-1991 distribution note 71 Rothstein & Yoon 2008+1.27
42941987 to 1988 distribution+1.53
45981987 to 1988 distribution
+2.07

From the above data, our best estimate is LSAT takers had a mean score of 32.6 with an SD of 6.3.

In this article I once again try to convert these scores to IQ but this time using equipercentile equating, a technique in which I will map LSAT scores to IQ by equating both distributions in a sample that took both tests.

I am aware of only nine people with both reported LSAT scores on this scale, and reported scores on tests that can be converted to IQ. Some of these are from famous people (Barack Obama, Eliot Spitzer, Lion of the Blogospher) but most are from the Omni magazine sample used to norm Ron Hoeflin’s Mega Test, though only when there was no score from a more established test (SAT/GRE) with which which to pair the LSAT score, did I use the Mega Test score

PersonLSAT score Score on another testIQ equivalent of other test (U.S. norms, sigma 15)Source
Eliot Spitzer481590 on Old SAT170wikipedia (2024-09-24)
Lion of the Blogosphere461410 on Old SAT143Discussion on X.com (2024-06-02)
Barack Obama43.5 (42 to 45)128 on WISC (Wechsler Intelligence Scale for Children)124 after adjustment for suspected Flynn effectSource for LSAT score
Source for WISC score
Mega Test taker431400 old GRE141Omni sample
Mega Test taker421540 old SAT157Omni sample
Mega Test taker421360 old SAT139Omni sample
Mega Test taker411370 old SAT140Omni sample
Mega Test taker341290 old SAT139Omni sample
Mega Test taker346 on the Mega Test125Omni sample

For these nine individuals, the correlation between the LSAT and another IQ test they took was about 0.53. Their average LSAT score is 41.5 (SD = 4.5) and their average IQ is 142 (SD = 13).

Thus the formula for converting LSATs from this era to IQ (U.S. norms):

IQ = [(LSAT – 41.5)/4.5](13) + 142

Recall from above that the mean LSAT scores of LSAT takers was 32.6 (SD = 6.3). Thus on a scale where Americans on the whole have an average IQ of 100 (SD = 15), the law school bound elite had averaged IQ 116 (SD 18.9). An average IQ of 116 sounds plausible given that this was just over the mean for college grads in the 1980s but the SD of 18.9 is surprisingly high and may be an artifact of some kind.