In choosing appropriate education, it is often needed to compare the ability of a highly gifted child of a younger age with a moderately gifted class of an older age. Before now, this has been basically guesswork.

I have found a better approximation: convert a given IQ at a given age to an absolute measure of intelligence, the Stanford-Binet 5 CSS score or the identical Woodcock-Johnson III or IV W-score, then convert that score back to an IQ score for a given age (or an age for a given IQ score).

Here's my blog post: Converting IQ at a Given Age to an Absoloute (Rasch) Measure of Intelligence .

Here's the graph that lets you do it:


(which may not work, it's also at the top of the blog post)

Updated research on this published on Substack: Skipping Grades and Other Gifted Acceleration and Real measures of intelligence


"This graph comes from data from the Woodcock-Johnson IV Technical Manual, p. 279-280. (large pdf, link opens in new window.). Rasch measure Intelligence vs Age.pdf [Google Drive, single-page PDF (71kB)]" (See "Real measures of intelligence" link above for the live links)

This spreadsheet allows you to figure out answers to placement, comparison and acceleration questions that were practically impossible before. One can convert among: adult IQ, child IQ, child percentile, W-score (absolute intelligence measure on the WJ-IV similar to CSS on SB5), future or past scores at different ages, and even find a child's percentile in a class of a different age, average IQ.

From the "Skipping Grades and Other Gifted Acceleration" post:


Children's adult IQ equivalents

Children's ratio (mental over chronological age) IQ equivalents

Grade Skip Tables - Maximum recommended acceleration for different class average percentiles: 15%, 30%, 50%, 67%, 80%, 90%, 95%; here's the one for an 80th- percentile average school or class:


College readiness - how does your child measure up against ideal academics?