What does an IQ of 128 mean?
Above the central range on the reference scale, at approximately percentile 96.9.
- IQ score
- 128
- Percentile
- 96.9
- At or above
- 3.1%
Normal reference · mean 100 · SD 15. These are calculated values, not observed starp population ranks.
Where 128 sits on the IQ scale
A score of 128 is 28 points above the mean. Dividing by the standard deviation gives (128 − 100) ÷ 15 = 1.87. The normal cumulative distribution converts that standardized position into percentile 96.9.
This is above the central 85–115 interval and below two standard deviations above the mean. It indicates a higher position on this reference scale; it is not a percentage of questions answered correctly or a prediction about a particular career.
How common is a score of 128?
Approximately 3.1% of this model lies at or above 128—about 1 in 32. This is a cumulative share, not the chance of scoring exactly 128. A continuous model does not assign a positive probability to one exact value.
Compared with IQ 115, the reference percentile is 12.77 percentage points higher. Equal IQ-point gaps do not create equal percentile gaps: the middle of the bell curve contains more area than its ends.
Compare nearby scores
Compare 123 and 128 or calculate 128 on another scale. A small difference between test results is not automatically a meaningful change.
How this relates to starp
starp's current scoring map does not produce exactly 128. Its neighboring results are 126 for 27 correct answers and 132 for 28 correct answers out of 30. This guide explains the conventional scale value 128; it does not invent an intermediate starp result.
See the scoring method and how raw scores differ from IQ estimates.
Questions about IQ 128
Is 128 a good IQ score?
128 is above the reference mean of 100. It is a higher score on that scale, but a number alone cannot establish a specific skill profile or predict success.
What percentile is an IQ of 128?
On a normal scale with mean 100 and standard deviation 15, 128 corresponds to approximately percentile 96.9. Around 3.1% of that model lies at or above it. Use an assessment's own norms for an actual reported rank.
Does an IQ of 128 mean 128% correct?
No. IQ is a scaled score. Percentage correct depends on the questions and scoring rules; percentile describes a relative position. These three quantities are not interchangeable.
Method: NIST's normal-distribution formula. Percentiles here are calculated reference values, not observed starp population ranks. About starp scoring.