IQ 55

An IQ of 55 is 45 points below the average of 100, or 3.00 standard deviations. This site classes it as Below Average. About 0.1% of people score at or below 55, which in a class of 30 is roughly one person or fewer. It sits 15 points below 70.

A score under 70 on a single online test does not mean anything clinical. Only a qualified professional, such as a clinical or educational psychologist, can assess that, using supervised tests and a look at everyday functioning.

IQ tests measure a narrow slice of thinking: spotting patterns, holding rules in mind and working fast under time pressure. They do not measure practical skill, kindness, reliability, craft or creativity, which are the things most people notice about you day to day.

Retest gains of a few points are well documented once a format is familiar. First attempts at any unfamiliar kind of test tend to be the least representative.

A 55 from one online test is best read as a range, not a point. Even a well-built, supervised test has a margin of error of roughly 5 points either side, so the same person could reasonably score anywhere from about 50 to 60. That spans the 0.04th to the 0.38th percentile.

Professional assessments combine several subtests (verbal, visual, memory and speed) and look at the pattern between them, not just one total. A single online total cannot show that pattern.

Your screen, your connection, background noise and interruptions all affect a timed test. A phone in a busy room is a very different test from a quiet desk.

Near 55 the curve is steep, so a few points change your percentile a lot. Going from 55 to 58 would lift you from the 0.13rd to the 0.26th percentile. These are the usual reasons scores swing:

• Stress and mood. Worry takes up working memory. People who feel anxious about tests often score below their usual level.
• Language. Questions that rely on words or written rules favour native speakers. Visual puzzles reduce this effect but do not remove it.
• Familiarity. People who have seen matrix-style puzzles before tend to do better on them. That is a practice effect, not a change in underlying ability.

On a bell curve with a mean of 100 and a standard deviation of 15, about 0.1% of people score 55 or lower. Applied to whole populations:

About 0.1% of people score 55 or lower, compared with 0.0% at 50 or lower and 0.4% at 60 or lower. Five points here changes the share by about 0 percentage points.

What your 55 could really be. Treat any single score as the centre of a range. For a good supervised test, about 5 points either side is typical, so 55 really means somewhere from 50 to 60. Online tests are less precise than that.

Which scale was it on? A 55 reported on an SD 16 scale converts to about 58 on the usual SD 15 scale, and one from an SD 24 scale (seen in some Cattell-style results) to about 72. Check which scale your score report used.

Nobody famous has a verified IQ in most cases, and retrospective estimates are only made for a narrow group.

No historical figure on this site has an estimate close to 55. Retrospective estimates cluster between about 115 and 250 because they are only made for people with exceptional achievements. That is a selection effect, not a sign that famous or successful people cannot score 55.

Nearby scores and the round-number landmarks, so you can see how quickly the percentile changes around 55. Every row links to that score's page.