IQ Score Converter
Convert a score between the common scales used in psychology and education: IQ with standard deviation 15, 16 or 24, z-score, T-score (mean 50, SD 10), Wechsler scaled score (mean 10, SD 3), stanine and percentile. Example: an SD 16 score of 132 is a z-score of 2.00, an SD 15 score of 130, a T-score of 70 and the 97.7th percentile.
For percentile enter 0.01 to 99.99.
Show steps
How to use the IQ Score Converter
- Enter the score you have.
- Select which scale it is on, for example IQ with SD 16 or a T-score.
- Press Calculate to see the same score on every scale.
- Use the percentile as the common language when comparing tests.
Formula and method
Every standard score is a rescaled z-score. z = (score - mean) / SD, and a new score is meannew + SDnew x z. Common pairs are IQ (100, 15), older Stanford-Binet (100, 16), Cattell (100, 24), T-score (50, 10) and Wechsler subtest scaled score (10, 3).
Common standard-score scales
| Scale | Mean | SD | Used for |
|---|---|---|---|
| IQ (Wechsler) | 100 | 15 | WAIS, WISC, most modern tests |
| IQ (older Stanford-Binet) | 100 | 16 | 1937-1960 forms |
| IQ (Cattell) | 100 | 24 | Cattell Culture Fair and similar |
| T-score | 50 | 10 | Personality and behavior scales |
| Scaled score | 10 | 3 | Wechsler subtests |
| z-score | 0 | 1 | Statistics |
Why conversion matters
Reading “IQ 148” without knowing the test is risky. On an SD 24 scale that is z = 2.00, the same rank as 130 on an SD 15 scale. Converting to z-scores or percentiles shows when two numbers describe the same standing. The IQ percentile calculator shows the rank in more detail.
About stanines
A stanine is a nine-point scale with mean 5 and SD about 2. It is computed here as 2z + 5, rounded and limited to 1-9. Official stanine tables use fixed percentile bands, so they may differ by one at boundaries.
Limits and responsible use
Important: this is a statistics tool, not an IQ test. It converts a score you already have into a percentile and a descriptive band using a normal (bell-curve) model. Clinical IQ scores come only from a standardized test given and interpreted by a qualified psychologist, and online quizzes give estimates at best.
Frequently asked questions
What is 130 on SD 15 in SD 16?
About 132 (z = 2.00).
What is an IQ of 100 as a z-score?
Zero, since 100 is the mean.
What is IQ 115 as a T-score?
60, one standard deviation above the mean.
Are SD 15 and SD 16 IQ scores interchangeable?
Not exactly. They agree at 100 and drift apart as you move away from average.
What is a scaled score of 13?
z = 1.00, equal to IQ 115 on an SD 15 scale and the 84th percentile.
Can I convert any online IQ result?
Only if you know the scale the site used, and even then the result is only as reliable as the test.
Sources
- Intelligence quotient (Wikipedia)
- IQ classification (Wikipedia)
- Standard score (Wikipedia)
- Normal distribution (Wikipedia)
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