Should You Retake an IQ Test? When & Why It Makes Sense

Understanding Practice Effects

One of the most important concepts to understand before retaking any IQ test is the practice effect. This refers to the tendency for scores to improve on a second administration of the same test, simply because the test-taker is now familiar with the format, question types, and testing procedures.

Research on practice effects shows the following patterns:

• Typical score gain: When retaking the same IQ test within a few weeks to a few months, most people score approximately 3 to 8 points higher on the second attempt, even without any specific studying or training.
• Gains are largest on timed tests: Performance on timed subtests improves more than on untimed subtests, because test-takers become more efficient at managing their time once they know what to expect.
• Gains diminish with different tests: If you take a different IQ test the second time (for example, switching from the WAIS to the Stanford-Binet), practice effects are smaller because the specific questions and format differ, though some transfer of general test-taking skills still occurs.
• Gains diminish over time: The longer you wait between test sessions, the smaller the practice effect. After a year or more, the practice effect is substantially reduced.

Because of practice effects, a higher score on a retest does not necessarily mean your "true" intelligence has increased. It may simply reflect your increased comfort with the testing format. Professional psychologists account for practice effects when interpreting retest scores.

When Retaking an IQ Test Makes Sense

There are several legitimate reasons to retake an IQ test:

• Poor testing conditions: If you were sick, exhausted, extremely anxious, distracted by noise, or dealing with a personal crisis during the first test, your score may not reflect your true cognitive ability. Retaking the test when you are well-rested and calm can provide a more accurate baseline.
• Technical problems: If you experienced a computer crash, misunderstood the instructions, or accidentally skipped questions on an online test, a retest is clearly warranted.
• Significant life changes: If you have undergone treatment for a condition that was affecting your cognition (such as depression, sleep apnea, or a nutritional deficiency), retesting after treatment can show whether your cognitive performance has improved.
• Educational or clinical requirements: Some educational programs, gifted placements, or disability determinations require up-to-date testing. If your previous test results are several years old, a retest may be necessary. Learn more about how this applies to children.
• Curiosity and self-assessment: For online tests like ours, there is no clinical downside to retaking the test. It can be an interesting exercise to see how consistent your scores are across attempts.

Typical Score Variation on Retakes

Even without practice effects, IQ scores naturally vary from one testing session to another. This variation is a normal property of any measurement tool and does not mean anything is wrong with you or the test. Here is what research tells us about score stability:

• Test-retest reliability: Major IQ tests like the WAIS-IV and Stanford-Binet 5 have test-retest reliability coefficients of approximately 0.90 to 0.95 for full-scale IQ. This is very high, but it still allows for meaningful score fluctuations.
• Standard error of measurement (SEM): For most major IQ tests, the SEM is approximately 3 to 5 points. This means your "true" score likely falls within about 3 to 5 points of your obtained score in either direction. A score of 112 might reflect a true ability anywhere from roughly 107 to 117.
• Typical variation: It is normal for your score to fluctuate by 5 to 10 points between testing sessions, even on the same test under similar conditions. Fluctuations of up to 15 points, while less common, are not unheard of.
• Extreme scores are less stable: Very high and very low scores tend to regress toward the mean on retest. If you scored 145 on your first attempt, your score on a second attempt is statistically more likely to be somewhat lower (though still high) than to be even higher. This is a mathematical phenomenon called regression to the mean, not a sign of declining intelligence.

These variations are precisely why psychologists report confidence intervals rather than single numbers, and why no serious professional would rely on one test score to make important decisions. For more on the precision of IQ testing, see our guide on IQ test accuracy and limits.

How Long to Wait Between Tests

The optimal waiting period between IQ tests depends on your purpose and the type of test:

• Same professional test (WAIS, Stanford-Binet): Most psychologists recommend waiting at least one year before retaking the same professional IQ test to minimize practice effects. Some recommend two years for the most accurate results.
• Different professional test: If you switch to a different IQ test (for example, from the WAIS to the Stanford-Binet), a shorter interval of six months to a year may be acceptable, since practice effects transfer less between different instruments.
• Online IQ tests: For informal online tests like the one on this site, there is no mandatory waiting period. However, if you retake the same online test immediately, your familiarity with the specific questions will artificially inflate your score. Waiting at least a few weeks and ideally trying a different version or test gives you a more meaningful result.
• Clinical retesting: In clinical settings (such as tracking recovery from brain injury or evaluating treatment for cognitive impairment), psychologists use specialized techniques and alternate test forms to account for practice effects when retesting at shorter intervals.

Why Scores May Differ Between Different Tests

If you take multiple IQ tests and get different scores, this is normal and expected. Different tests can yield different scores for several reasons:

• Different abilities measured: Some tests emphasize nonverbal reasoning (like Raven's Progressive Matrices), while others include verbal, spatial, and processing speed components (like the WAIS). Your score reflects your strengths relative to what each test measures. Read about different types of IQ tests to understand these differences.
• Different norming groups: Tests are normed on different populations at different times. A test normed in 2000 may give you a slightly higher score than one normed in 2020, due to the Flynn Effect.
• Different standard deviations: The Wechsler tests use a standard deviation of 15, while the Stanford-Binet uses 16. This means a score of 130 on the Wechsler is equivalent to about 132 on the Stanford-Binet.
• Online vs. professional tests: Online tests typically have less precise measurement than professionally administered tests. If you scored 120 on an online test, your score on a professional test could realistically be anywhere from 110 to 130. See our comparison of online vs. official IQ tests.

The best way to get an accurate, reliable IQ estimate is through a professionally administered test in a controlled setting. But if you want a quick, informal estimate, our free online IQ test is a good starting point.