IQ 77: what it means
An IQ of 77 is higher than about 6.3% of people, roughly 1 in 16 at or below, in the borderline or "very low" range. Before you read too much into a single score, think about the conditions: a short night is one of the most common reasons for an off day on a timed test.
77 on the IQ bell curve
An IQ of 77 is 23 points below the average of 100, or 1.53 standard deviations. About 6.3% of people of the same age score lower, the shaded sliver at the far left of the curve below.
On a test with a standard deviation of 16, such as older Stanford-Binet editions, the same result would be about 75, and on the Cattell scale, which uses 24, about 63. Why scales differ.
Reading an IQ of 77
A meta-analysis of 70 studies of short-term sleep deprivation found that the biggest effects are on attention and speed: lapses of attention were the most affected measure of all. Reasoning accuracy itself was barely affected in those studies, but on a timed IQ test, slower and patchier attention still costs points, because unanswered questions count as wrong.
So a 77 after a late night tells you less than a 77 after a good one. If your score came from a professional assessment, the psychologist will have noted how alert you seemed. If it came from an online test, take it again in the morning and see what changes; a result that moves a lot was never very solid.
How an IQ of 77 is classified
Different tests and manuals use different words for the same score, and the words have changed over time. Here is where 77 falls on each of the systems you are most likely to meet.
Sources: American Psychiatric Association, DSM-5 fact sheet on intellectual disability; World Health Organization, ICD-11, 6A00 disorders of intellectual development; Peltopuro, M. and others (2014), "Borderline intellectual functioning: a systematic literature review", Intellectual and Developmental Disabilities, 52(6), 419–443. WISC-V descriptors from Pearson's interpretive reports, as on our good IQ score guide.
Borderline intellectual functioning and an IQ of 77
Scores from roughly 70 to 85 are often described as borderline intellectual functioning. It is not a diagnosis of intellectual disability: most people in this range live independently, work and raise families. But a 2014 systematic review of 49 studies found that the group faces more neurocognitive, social and mental health difficulties than average, and called it "almost invisible" in research and services.
On a perfect bell curve, about 13.6% of people score between 70 and 85, so this is far from rare. People in the range often learn best with clear, concrete instructions, worked examples and extra time for new or written tasks, and often do well in practical, hands-on work.
Source: Peltopuro, M. and others (2014), "Borderline intellectual functioning: a systematic literature review", Intellectual and Developmental Disabilities, 52(6), 419–443.
What military aptitude rules say about 77
The US armed forces don't use IQ tests: they use the Armed Forces Qualification Test (AFQT), scored as a percentile of young adults. On the IQ scale, 77 is at about the 6th percentile, which would correspond to AFQT Category V. The comparison is only rough, because the AFQT tests word knowledge, reading and maths, which depend heavily on schooling.
Sources: 10 U.S.C. § 520 (2024 edition); US Department of Defense, Population Representation in the Military Services; history of the 1966 Project 100,000: Greenhill, K. M., "Don't dumb down the army", Belfer Center, Harvard Kennedy School.
Before you trust a 77
Low scores are the most fragile results on any test, because almost everything that goes wrong on the day pulls a score down. Common reasons include:
- Running out of time. On timed tests, including ours, an unanswered question counts as wrong.
- Nerves. A review of 238 studies found test anxiety consistently linked with lower scores.
- Tiredness. Sleep loss hits attention and speed hardest, which costs points against the clock.
- Language and format. Taking a test in a second language, on a small screen or in an unfamiliar format can lower a result without saying anything about reasoning.
What a 77 means on our test
The Assessivo test moves in steps of about 2.5 points, so it can't give exactly 77: the nearest results are 75 (8 correct) and 78 (9 correct). Every question has four options, so someone guessing every answer at random averages nine correct, a score of 78. That is within what pure guessing produces: a guesser lands at or below this level in about 44% of attempts. Read it as "not measured yet" rather than a verdict, and retake the test rested, with time to spare.
If any of this sounds like your session, retake the free IQ test when you are rested and have 25 quiet minutes. A score that moves a lot between attempts was never very solid.
Sources: von der Embse, N. and others (2018), "Test anxiety effects, predictors, and correlates: a 30-year meta-analytic review", Journal of Affective Disorders, 227, 483–493; Lim, J. and Dinges, D. F. (2010), "A meta-analysis of the impact of short-term sleep deprivation on cognitive variables", Psychological Bulletin, 136(3), 375–389. Guessing figures are worked out from the binomial distribution for 36 four-option questions.
What is the mental age for an IQ of 77?
The first IQ tests, for children, described performance as a "mental age": the age whose typical performance a child matched. IQ was mental age divided by real age, times 100. Run that old formula backwards and you get the figures below, for children only.
| Child's age | Performs like a typical child of about |
|---|---|
| 6 | 4 years 7 months |
| 8 | 6 years 2 months |
| 10 | 7 years 8 months |
| 12 | 9 years 3 months |
| 14 | 10 years 9 months |
For adults the idea doesn't work, which is why David Wechsler replaced it in 1939 with today's method: compare each person with others of the same age. An adult who scores 77 has an adult's knowledge, interests and experience. The score only says how their test performance compares with other adults'.
How common is an IQ of 77?
Line up 100 people of the same age and about 6 would score 77 or lower; the orange dot marks the place. In a school of 1,000 pupils, you would expect about 63 at or below this level.
The bar shows the likely range on a professional test, about five points either way: 72 to 82, from the 3rd to the 12th percentile.
How 77 compares with nearby scores
| IQ | Percentile | Classic label | Score this low or lower |
|---|---|---|---|
| 67 | 1st | Extremely low | 1 in 72 |
| 72 | 3rd | Borderline | 1 in 32 |
| 77 | 6th | Borderline | 1 in 16 |
| 82 | 12th | Low average | 1 in 9 |
| 87 | 19th | Low average | 1 in 5 |
Questions about an IQ of 77
What percentile is an IQ of 77?
An IQ of 77 is at about the 6th percentile: it is higher than about 6.3% of people of the same age, and roughly 1 person in 16 scores this low or lower.
Is 77 a low IQ?
Yes. 77 is 23 points, or 1.53 standard deviations, below the average of 100. On the classic Wechsler labels it is borderline, and the current children's Wechsler test calls it very low. A single score is an estimate with a margin of error of about five points, so 77 is best read as roughly 72 to 82.
Is 77 IQ an intellectual disability?
No. 77 is above the range usually associated with intellectual disability, which is about 70 or below. It falls in the range sometimes called borderline intellectual functioning, which is not a disability in itself.
What is the mental age for an IQ of 77?
Mental age is an idea from the earliest tests for children. By the old formula, a 10-year-old scoring 77 would perform like a typical child of about 7 years 8 months. For adults it has no meaning: modern IQ tests compare adults with other adults, and an adult who scores 77 is not like a child.
Does lack of sleep affect IQ test scores?
It can. A meta-analysis of 70 studies found that short-term sleep loss hurts attention and speed most, which matters on timed tests even when reasoning accuracy holds up. For the most accurate result, take a test rested and at a time of day when you are alert.
Related: the IQ range chart, what counts as an average IQ, what IQ measures and misses and how to tell if an online IQ test is accurate.
An IQ test arrives at a score like 77 by combining several kinds of task. Learn more about spatial reasoning, verbal reasoning, processing speed, fluid vs crystallized intelligence and abstract reasoning, or try the free pattern recognition test.
Information and support
If a professional assessment has given you, your child or someone you care for a score like 77, these organisations explain what it means in practice and what help is available.
Want a second reading?
Take the free Assessivo IQ test when you are rested and have 25 quiet minutes: 36 questions, and your estimated score and percentile as soon as you finish.
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