Quick answer: Mensa membership needs a top 2% score (about IQ 130) on a supervised test. The free online tests do not count towards that. Altto’s free Top 2% challenge is a practice test of the same kind of reasoning, and it is honest about what it can and cannot tell you.
What Mensa actually requires
Mensa is a society for people who score in the top two per cent of the population on an approved intelligence test. Its UK page says the same thing: membership needs an IQ in the top two percent, shown either by a supervised test or by prior evidence such as an educational psychologist’s report or a professionally given IQ test. Nothing taken unsupervised in your own browser can stand in for that, however well written the test is.
The Mensa UK options, and what they cost
This is what Mensa UK’s own page listed on 12 November 2026. Check it before you book, because prices and formats change.
| Option | Cost | Time | Supervised? | What you get |
|---|---|---|---|---|
| Online workout | Free | 15 minutes | No | An indication only; no IQ score |
| Mensa Home Test | £15 | 45 minutes | Not stated | An indicative score |
| Online supervised test | £49 | 1½ hours | Yes, by a proctor online | A result Mensa can use for membership |
| In-person supervised test | £49 | 2¼ hours | Yes, at a test centre | A result Mensa can use for membership |
| Prior evidence | £49 | Not applicable | Not applicable | Your existing report or test result is reviewed (4–6 weeks) |
Source: mensa.org.uk/iq-test, read 12 November 2026. Candidates must be over 10½ for the supervised tests, and applicants must live in the UK or Ireland.
The free online Mensa tests
Two free online tests carry Mensa’s name, and both say plainly that they cannot get you in.
- The Mensa IQ Challenge (on mensa.org) is 35 puzzles in 25 minutes. It is for entertainment only. If your score is below 100 it says the score is outside the range the test can currently measure.
- Mensa Norway’s online test (on test.mensa.no) is 35 problems in 25 minutes, with scores between 85 and 145. It says it is not a substitute for a professional intelligence test.
Both are short and made of picture puzzles. That makes them good for seeing whether you enjoy this kind of question, and poor for settling whether you are near the top-2% line.
Where Altto’s tests fit
Altto’s IQ test is free, needs no sign-up and shows your full score and breakdown the moment you finish. It has four lengths:
- Quick (10 questions), Standard (20) and Complete (40), which span the whole range from easy to very hard.
- The Top 2% challenge (30 questions, 35-minute limit), added on 12 November 2026. Most of its puzzles sit in the hard half of the range, because that is where the top-2% line is. Its result also says how likely it is that your true score is 130 or more.
The point of the challenge is precision where it matters. In simulated tests (made-up test-takers whose true scores we set in advance, not real people), here is the typical error of the score each test gives, in IQ points, for someone whose true score is 100, 130 or 140:
| Test | True score 100 | True score 130 | True score 140 |
|---|---|---|---|
| Quick test (10 questions) | about 8.5 | about 11.1 | about 14 |
| Standard test (20 questions) | about 6.4 | about 8.2 | about 9.5 |
| Complete test (40 questions) | about 5.1 | about 6.1 | about 7 |
| Top 2% challenge (30 questions) | about 9.2 | about 5.3 | about 5.6 |
At 130 and above the challenge is the most precise of the four. Below about 100 it is the least precise: it has few easy questions, and random guessing on it averages about 82. If you expect to score under 100, the Standard test is the better choice. The method and its limits are on our how the IQ test is scored page.
What an online test cannot do
- It cannot be supervised. Nobody checks who took it, how long you took, or whether you looked anything up. That is the whole reason Mensa and clinicians discount it.
- It has not been formally norm-referenced. Altto’s difficulty ratings are careful estimates, not figures from a formal study of a representative sample. We are now logging anonymous question-by-question results to check them against real answers, and will publish what we find.
- One attempt is one noisy reading. Retaking a few days later gives a second reading, and the two together tell you more than either alone.
If a result gets you curious about the real thing, the supervised test is the next step, and Mensa UK’s page above is where to book it.
Practise the right way
Try the Top 2% challenge somewhere quiet, in one go, without looking anything up. Read your breakdown by area to see which kinds of puzzle cost you the most time, then use the free practice puzzles by area on the IQ test page. More free tests are on the tests page, and our guide to which online IQ tests are actually free covers the paid-result traps to avoid.
Mensa is a trademark of its owners. Altto is not affiliated with or endorsed by Mensa.
Frequently asked questions
Can I join Mensa with an online IQ test score?
No. Mensa asks for a score in the top 2% from a supervised test (or from prior evidence such as an educational psychologist’s report). Online tests, including Mensa’s own free online ones, are for practice and entertainment and do not qualify you. Altto’s test is the same: it gives an estimate and cannot be used to join Mensa.
How much does the Mensa test cost in the UK?
On Mensa UK’s page (checked 12 November 2026) the online workout is free and gives no IQ score, the Mensa Home Test is £15, and the supervised tests (online with a proctor, or in person at a test centre) are £49 each. Applicants must live in the UK or Ireland. Prices and options change, so check Mensa’s own page before you book.
What IQ do you need for Mensa?
A score in the top 2% of the population on an approved supervised test. On the usual scale (average 100, standard deviation 15) that is about 130. Some older tests use a different spread, so the same top-2% line can read as a different number on them, which is why Mensa describes it as a percentile rather than a fixed IQ.
How many questions are in the Mensa IQ Challenge?
35 puzzles in 25 minutes, getting harder as you go. It is offered for entertainment, will not qualify you for Mensa, and says a score below 100 is outside the range it can measure. Mensa Norway’s separate online test has 35 problems in 25 minutes and reports scores from 85 to 145.
Is there a free practice test for the Mensa test?
Mensa’s own free online options are the workout on Mensa UK’s site and the Mensa IQ Challenge on mensa.org. Altto’s free Top 2% challenge is another way to practise the kinds of puzzle involved. None of them tells you how you would score on the supervised test.
Is Altto connected to Mensa?
No. Altto is an independent site. Mensa is a trademark of its owners, and Altto is not affiliated with or endorsed by Mensa. We name Mensa only to describe what it offers and how its tests compare with free online ones.