Understanding Standard Deviations (SD)
The key to understanding IQ percentiles is the standard deviation (SD). With a mean of 100 and SD of 15:
- +1 SD = IQ 115 → top 16% of population
- +2 SD = IQ 130 → top 2.3% (1 in 44 people)
- +3 SD = IQ 145 → top 0.13% (1 in 741 people)
- +4 SD = IQ 160 → top 0.003% (1 in 31,560 people)
- +5 SD = IQ 175 → approximately 1 in 3.5 million
- +6 SD = IQ 190 → approximately 1 in 1 billion
Complete IQ Percentile Table
| IQ Score | Percentile | Rarity (1 in X) | SD Above Mean |
|---|---|---|---|
| 100 | 50th | 2 | 0 |
| 105 | 63rd | 3 | 0.33 |
| 110 | 75th | 4 | 0.67 |
| 115 | 84th | 6 | 1.0 |
| 120 | 91st | 11 | 1.33 |
| 125 | 95th | 20 | 1.67 |
| 130 | 97.7th | 44 | 2.0 |
| 135 | 99.0th | 100 | 2.33 |
| 140 | 99.6th | 261 | 2.67 |
| 145 | 99.87th | 741 | 3.0 |
| 150 | 99.95th | 2,330 | 3.33 |
| 155 | 99.98th | 6,210 | 3.67 |
| 160 | 99.997th | 31,560 | 4.0 |
| 165 | 99.9992nd | 130,000 | 4.33 |
| 170 | 99.9998th | 600,000 | 4.67 |
| 175 | 99.99997th | 3,500,000 | 5.0 |
| 180 | 99.999994th | 17,000,000 | 5.33 |
| 190 | ~99.9999999th | ~1 billion | 6.0 |
| 200+ | Theoretical | Beyond known population | 6.67+ |
What Each Level Means in Practice
IQ 100–115: Average to Above Average
This range covers most people. At 100 you're at the exact midpoint. At 115 you're scoring better than 84% of people — roughly equivalent to what's needed for success in most professional careers. Most college graduates fall in this range.
IQ 120–130: Superior Intelligence
You're now in the top 9–2% of the population. People in this range tend to excel academically, grasp complex concepts quickly, and often pursue careers in law, medicine, science, engineering, or management. Many successful professionals cluster here.
IQ 130–145: Gifted to Highly Gifted
The gifted range begins at 130. At 145, you're 1 in 741 — there are roughly 10 million such people on Earth. Richard Feynman reportedly scored around 125 on a childhood IQ test, yet won the Nobel Prize — a reminder that domain-specific genius can outstrip raw score.
IQ 145–160: Genius Territory
At 160, you share your cognitive level with estimated historical giants. Stephen Hawking and Albert Einstein are both estimated at around 160. Visit the IQ 160 page for more examples. At this level, roughly 1 in 31,000 people match or exceed your score.
IQ 160–200+: Ultra-High Range
Beyond 160, formal tests struggle to differentiate reliably. Terence Tao (225–230), William James Sidis (250–300 estimated), and Marilyn vos Savant (228 at age 10) are the most famous names in this stratosphere. At these levels, we're talking about potentially 1 person in millions or billions — individuals whose cognitive abilities operate in a fundamentally different register.