Convert IQ ↔ Stanine
How the conversion works
IQ and Stanine 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.
- Stanine: 1-9 scale with mean 5 and standard deviation 2. Each stanine band covers a fixed percentile range of the normal distribution. Stanines were developed by the US Air Force during WWII as a single-digit format for cognitive testing.
IQ-equivalent = (target − meantarget) / SDtarget × 15 + 100
target-equivalent = (IQ − 100) / 15 × SDtarget + meantarget
Common IQ ↔ Stanine reference table
| IQ | Stanine | Percentile |
|---|---|---|
| 70 | 1 | bottom 4% |
| 80 | 2 | 4-11% |
| 90 | 4 | 23-40% |
| 100 | 5 | 40-60% |
| 110 | 6 | 60-77% |
| 120 | 7 | 77-89% |
| 130 | 8 | 89-96% |
| 140 | 9 | top 4% |
Important caveats
- Stanines are a coarser format than IQ; they round to one of 9 bands, so the conversion is approximate by design. The exact percentile-to-stanine cutoffs are defined by convention (4%, 7%, 12%, 17%, 20%, 17%, 12%, 7%, 4%).
- 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.
Related tools
IQ percentile calculator · IQ to Z-score converter · IQ to T-score converter · IQ score chart
Cite this converter
Editorial content and curation are released under CC BY-SA 4.0. This converter is part of the What's Your IQ educational resources.