Compare IQ scores
See the difference between two scores on the same scale.
Percentile 50
Percentile 84.13
Score B is 15 points higher, a difference of 34.13 percentile points.
This compares positions on one reference scale. It does not show a change in a person's intelligence or establish that two different tests are equivalent.
Understanding the difference
A difference in IQ points and a difference in percentile points are two ways to describe a gap. From 100 to 115 is 15 IQ points and about 34.13 percentile points on the default model. From 115 to 130 is also 15 IQ points, but about 13.59 percentile points.
Comparing repeat tests requires more than subtracting scores: measurement error, practice and testing conditions can affect the result. The comparison does not tell you whether a change is statistically reliable.
Use the right scale
The default is mean 100 and standard deviation 15. Scale settings also allow SD 16 or 24. These are mathematical conversions; they do not equate different tests or validate an online score.
The two input scores are interpreted on the same selected scale. If their original tests use different scales, check their documentation before comparing them.
Keep the context
starp uses a fixed score map calibrated with simulated assessments. These normal-model results do not establish a human population percentile for a starp score.
Browse every score from 70 to 160 · Percentile calculator · Read about percentiles
Method: NIST's normal-distribution formula. Percentiles here are calculated reference values, not observed starp population ranks. About starp scoring.