IQ to Z-score Score Converter

Convert IQ ↔ Z-score

How the conversion works

IQ and Z-score scores are normalised on bell-curve distributions. The conversion maps a person's standing in one distribution to the equivalent standing in the other.

• IQ: mean 100, standard deviation 15.
• Z-score: mean 0, standard deviation 1. Z = (raw score − mean) / SD. Z-scores express how many standard deviations a value is above or below the mean of its distribution.

IQ-equivalent = (target − mean_target) / SD_target × 15 + 100
target-equivalent = (IQ − 100) / 15 × SD_target + mean_target

Common IQ ↔ Z-score reference table

Important caveats

• IQ and Z-scores are mathematically equivalent representations of the same standing on a normal distribution. The conversion is exact (Z = (IQ − 100) / 15), not an estimate, because both use the same underlying scale.
• Extreme-tail conversions are less reliable because both tests have fewer calibration cases there.
• No score entered here is stored, submitted, or connected to an account.

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IQ percentile calculator · IQ to T-score converter · IQ to Stanine converter · IQ score chart