An IQ score of 198 falls into the Profoundly Gifted range on the standard intelligence scale (mean = 100, standard deviation = 15). This score is in the extreme right tail of the distribution — IQ scores above 160 are statistically very rare.
What an IQ of 198 means
An IQ of 198 is about 1 in 31 billion. Figures in this range, and higher, are attached to a few historical prodigies, such as William James Sidis, who entered Harvard at eleven. The numbers often quoted for him, 250 or more, are later estimates, not results of any test he took. His story is real and remarkable; the score is folklore. On the standard scale, a true 198 would be rarer than anyone who has ever been measured.
Where does an IQ of 198 rank?
On a standardized IQ test, a score of 198 places you higher than approximately 100.0% of the population. Intelligence scores follow a normal distribution — most people cluster near 100, and scores taper off sharply toward both extremes.
| Metric | Value |
|---|---|
| IQ score | 198 |
| Classification | Profoundly Gifted |
| Percentile | 100.0% |
| Rarity (out of 1,000) | ~1 in 1,000 score this high or higher |
| Standard deviations from mean | 6.53 |
IQ 198 in numbers
- Roughly 1 in 31,000,000,000 people score 198 or higher.
- That is 68 points above 130, the level most high-IQ societies use as their entry line.
- This is already in the highest classification band on the standard scale.
- Even on professionally administered tests a single result has a margin of error of about five points either way, so a measured 198 is best read as somewhere between 193 and 200.
On our free IQ test
None of the 3,834 people who completed our free IQ test between April and October 2026 scored exactly 198; 0.0% scored higher. People who choose to take an online IQ test are not a random sample of the population (our average is 114.5), so this shows where a score sits among other test-takers, not among everyone. More in our 2026 data study.
Which IQ tests produce a score of 198?
A score of 198 can be produced by any standardized intelligence test that uses the mean = 100, SD = 15 scale. The most widely used tests include:
- Wechsler Adult Intelligence Scale (WAIS) — clinical gold standard for adults.
- Stanford-Binet Intelligence Scales — oldest continuously-used intelligence test.
- Mensa admissions test — used by the Mensa society for membership selection.
- Cattell-Horn-Carroll (CHC) tests — most theoretically grounded modern framework.
- Our free IQ test — instant online estimate with the same scaling.
How to interpret an IQ score of 198
Scores above 145 are in the highly gifted to profoundly gifted range and become increasingly rare the higher you go. At this level individual differences within the range matter less than how the cognitive ability is directed — deep expertise, creativity, and sustained effort are what produce exceptional real-world outcomes.
IQ 198 in Context
| IQ Range | Classification | Population % |
|---|---|---|
| Below 70 | Extremely Low | ~2.2% |
| 70–79 | Borderline | ~6.7% |
| 80–89 | Low Average | ~16.1% |
| 90–109 | Average | ~50% |
| 110–119 | High Average | ~16.1% |
| 120–129 | Superior | ~6.7% |
| 130+ | Gifted / Very Superior | ~2.2% |
Factors That Influence Your Score
Your IQ score reflects a combination of genetic potential and environmental influences including education, nutrition, health, and the testing conditions themselves. Factors like fatigue, anxiety, unfamiliarity with the test format, and even the time of day can all affect performance. A single test score should be viewed as an estimate, and scores can vary by several points between testing sessions.
Nearby scores
Compare the major IQ tests
Which test produces the most accurate score depends on what you're trying to measure. These head-to-head comparisons break down the differences:
- WAIS vs Stanford-Binet — the two clinical heavyweights compared.
- Mensa vs WAIS — entry-test speed vs full clinical assessment.
- Stanford-Binet vs Mensa — which one actually gets you into Mensa.
- CHC vs Wechsler — modern cognitive framework vs the classic.
- Raven vs Cattell — non-verbal alternatives for cross-cultural testing.
Further reading
- What is a good IQ score?
- What does your IQ score mean?
- Average IQ by age
- Mensa requirements
- IQ test types compared
Want to find out your IQ score?
Take a free, comprehensive cognitive assessment modeled on clinical IQ tests.
Take the Free IQ TestFrequently asked questions
Is IQ 198 considered good?
Yes — an IQ of 198 is well above average and falls in the gifted range. It's higher than approximately 100% of the population and typically exceeds the Mensa International admission threshold (130 on SD-15 tests).
Can an IQ of 198 change over time?
IQ scores are relatively stable in adulthood but can shift modestly with education, engagement, sleep, and health. Short-term factors like stress and fatigue can move a single test result by 5–10 points in either direction — which is why we recommend comparing results across multiple sessions rather than reading too much into any single score.
What percentile is IQ 198?
An IQ of 198 corresponds to the 100.0th percentile on the standard bell curve — meaning it is higher than about 100 out of every 100 people.