How to read a GAI vs FSIQ gap on a Wechsler report
GAIvsIQ Laboratory
2026-09-07

This note explains a narrow reading: subtract two official composite scores that already appear on a WISC or WAIS report. It does not administer a test, does not look up Pearson conversion tables, and does not produce a diagnosis.

What the two numbers are

Full Scale IQ (FSIQ) is the usual single summary of the battery. The General Ability Index (GAI) keeps the reasoning composites and leaves out working memory and processing speed. When those two official scores differ, the gap is GAI minus FSIQ. A positive gap means the GAI sits above the Full Scale number; a negative gap means the reverse.

How to compute it

1. Open the printed or portal report.
2. Copy the official FSIQ and the official GAI exactly as printed.
3. Gap = GAI − FSIQ.
4. Read the size of the gap against ordinary practice bands. Do not treat the calculator output as a new IQ score.

A working calculator that only performs this subtraction (and the related GAI − CPI and index layout) is here:

https://gaivsiq.com/calculator

Limits

- This is not a Pearson, WAIS, or WISC product.
- It is not a re-test and not a clinical instrument.
- The result is not school, employment, or visa documentation.
- If a report does not print an official GAI, do not invent one from subtests unless you are qualified to use the publisher tables.

License

CC BY 4.0. You may share this note with attribution. The calculator at gaivsiq.com remains a separate tool.