Question
What is the lowest possible IQ score?
Short answer
There is no fixed lowest IQ. Each test has a floor, the lowest score its items and norms can measure, and floors differ between tests. On the standard scale, 55 is three standard deviations below the mean; only about 0.13% of people, roughly 1 in 740, score that low or lower.
Want your own number? The test is 25 visual puzzles, about 12 minutes, no sign-up.
Floors and ceilings
An IQ test can only separate people with the items it contains. Near the bottom of the scale, a person may miss almost every item, and the test can no longer tell how far below that point their ability lies. That point is the test's floor. Because different tests have different items and norms, their floors differ, just as their ceilings do (see the highest possible IQ).
How rare low scores are
On a scale with mean 100 and standard deviation 15, about 95% of people score between 70 and 130 and about 99.7% between 55 and 145 (the 68-95-99.7 rule). That leaves about 2.3% below 70 and about 0.13% below 55. The WAIS-IV labels 69 and below Extremely Low (Wikipedia: IQ classification). You can see the exact percentile of any score in the IQ score chart, for example IQ 70 or IQ 55.
Try one · Logical Reasoning
Which tile completes the second pair?
Tap the option you think is right, or show the answer.
Show the answer
The missing panel shows a small outlined circle, with small solid shapes: a triangle at the bottom-left corner (option 5).
How to solve it
- Compare the first two panels and name exactly what changed.
- The main shape and the small shapes swap forms: the main shape takes the form of the small ones, and the small ones take the form of the main shape.
- Nothing else changes.
- Apply the same change to the third panel: a small outlined triangle pointing up, with small solid shapes: a circle at the bottom-left corner.
- So the missing panel shows a small outlined circle, with small solid shapes: a triangle at the bottom-left corner.
That was 1 puzzle. The full test has 25.
A score is not a diagnosis
A low score on its own does not establish intellectual disability. The AAIDD definition requires significant limits in both intellectual functioning and adaptive behavior, beginning before age 22, and it treats a score of around 70, or as high as 75, as the range that indicates a significant limitation (AAIDD). Clinicians weigh measurement error and everyday skills together. See what IQ is considered intellectual disability.
Low scores on online tests
A low result on an online test is usually a reason to look at conditions first: distraction, fatigue, a small screen, unfamiliar puzzle types or rushing. An online estimate is not a clinical measure. If a result worries you, a supervised assessment by a psychologist is the way to get a reliable picture. See what IQ is considered low.
Sources
- 68-95-99.7 rule. Wikipedia. en.wikipedia.org/wiki/68%E2%80%9395%E2%80%9399.7_rule
- IQ classification. Wikipedia. en.wikipedia.org/wiki/IQ_classification
- Defining criteria for intellectual disability. American Association on Intellectual and Developmental Disabilities. www.aaidd.org/intellectual-disability/definition