On my other blog I wrote the following:

The SAT is said to correlate about as well with IQ as two different IQ tests correlate with one another.  In his book Real Education (pg 69-70), Charles Murray claims that only 17 year olds capable of getting an 1180+ on the post 1995 SAT (Critical Reading + Math) are true college material.  Although 35% of American 17 year olds take the SAT, he estimates that only 10% of 17 year would score 1180+ if all of them took it..  In other words, 1180+ is equivalent to an IQ of 120+.

In his book Coming Apart (pg 375) he estimates an SAT score of 1400 is equivalent to an IQ of 135.  From these two data points, we can create the following formula for converting SAT into IQ equivalents:

IQ = 39.545 + 0.068(SAT score)

Note, this formula only applies to the post 1995 SAT.  Before 1995 the SAT was much harder.

This formula works well for individuals, but should never be used to estimate the median IQ of a college.  This is because elite colleges select for SATs, so the estimated median IQ will be artificially inflated by a selection bias.

Now when I plug in a perfect SAT score of 1600 into this formula, I get an IQ of 148 (U.S. norms). The problem is, I just read that 453 students scored 1600 on the new SAT in 1996-7 (out of approximately 3,500,000 17 year olds in the United States). That means 1600 equates to an IQ of 154 (U.S. norms).

So drawing a line of best fit through this data point, in addition to the two I got from Charles Murray, gives the following revised formula:

IQ equivalent = 23.835 + 0.081(new SAT score)