Number Series Test
Five numbers follow a rule and the sixth is missing. A free online number series test — a number sequence test, if that is the name you know it by: 12 series, 4 options each, a few minutes, no account, everything generated and scored in your browser. Every answer is explained the moment you give it — right or wrong, you get the rule that produced the sequence, in its own numbers — and at the end the whole run is listed out: each series, what you picked, what the answer was, and why. The result itself is your count, your mean time and the rules that held you up.
Take the test
Find the rule behind the five numbers, then pick the sixth. Keys 1–4 work too.
5 10 20 40 80 ?
0
of 12 series solved
A clean run: the rules came apart quickly, including the two where the gaps between the numbers tell you nothing on their own. Time is the thing left to improve.
Most of the run came apart. What usually survives is the interleaved rule and the one where each number is the sum of the two before it — both hide behind an irregular gap.
About half. That is the ordinary shape of a first run on a format most people last met in an exam room; the rules repeat, so a second run tends to look different.
Fewer than half this time. One twelve-item run in a browser tab says nothing about you in general — it is a warm-up, and the same five rules come back on the next one.
- Same step
- — / 3
- Same multiplier
- — / 2
- Growing step
- — / 3
- Two series interleaved
- — / 2
- Sum of the two before
- — / 2
Each explanation holds for up to 4.3 s — click the card, or press Space or Enter, to move on sooner.
12 series, easy ones first, each one explained as soon as you answer. There is no time limit — the clock exists only so the result can tell you how long you took. Nothing is uploaded; it all stays in this tab.
Your answers, with the rule for each
Every series of the run you just took: what you were shown, what you tapped, what the answer was, and the rule behind it. The rules are read off the items themselves, so nothing here is a general description of the format — it is what these 12 were actually built from.
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Your answer Correct answer
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Your answer Correct answer
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Your answer Correct answer
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Your answer Correct answer
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Your answer Correct answer
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Your answer Correct answer
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Your answer Correct answer
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Your answer Correct answer
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Your answer Correct answer
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Your answer Correct answer
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Your answer Correct answer
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Your answer Correct answer
That was a single run. In the app it becomes a short daily session, with a Focus Index to show for it.
Point your camera at the code — the App Store opens.
What a number series test measures
Every series here has exactly one rule behind it. You are shown five numbers it produced and asked for the sixth — so the work is to infer the rule from instances and then apply it once.
Psychologists call that pattern induction, and it is the most common way of getting at fluid reasoning: solving something you were never taught a method for, as opposed to recalling something you learned. Number series have been a fixture of reasoning and IQ test batteries for a century, and of the aptitude tests employers hand out, for the practical reason that the format is compact, needs almost no language, and can be generated by the thousand without repeating itself — the same reasons it works here.
What it does not measure is arithmetic. The sums stay small on purpose; every series above is solvable in your head, and the moment you have the rule the last step is trivial. If a series beats you it is because the rule stayed hidden, not because the multiplication did.
The five rules you will meet
12 series to a run, drawn fresh each time from these five and served easy ones first. Each example below is a real draw from the same generator the test uses — the sixth term, the one the test withholds, is shown in color — and the explanation under it is written by the same function the test explains with, so these words cannot drift from what the instrument says. The card shows the first sentence of it while you play; the full note is what every row of the list under the run carries.
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Same step
2 5 8 11 14 17
Add 3 every time: 2 · 5 · 8 and on to 17. The gap between neighbors never changes, so once you have measured it the last term is arithmetic rather than insight.
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Same multiplier
9 18 36 72 144 288
Multiply by 2 every time: 9 · 18 · 36 and on to 288. The giveaway is the shape of the gaps — they grow as fast as the numbers do, which addition cannot produce.
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Growing step
6 8 13 21 32 46
The step itself grows — +2, +5, +8, +11, +14 — so the sixth term is 46. Irregular at first glance, perfectly regular one level down: take the differences of the differences and the rule is in front of you.
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Two series interleaved
6 7 12 9 18 11
Two series taking turns: 6 · 12 · 18 steps +6, 7 · 9 · 11 steps +2. Consecutive gaps tell you nothing here; every other number tells you everything.
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Sum of the two before
9 10 19 29 48 77
Each term is the sum of the two before it: 29 + 48 = 77. Fibonacci’s own rule, started from whichever pair the draw handed you — sometimes the famous one, more often not, which is why it does not always look like Fibonacci.
How to read your result
Three numbers, and they are worth more together than apart.
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The count
How many of the 12 you solved. With 4 options per series, tapping at random is worth about 3 of them, so the count only starts saying something above that — and a run of guesses shows up in the time as plainly as in the number.
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The per-rule tally
Which rules actually came apart. Every same-step series solved and both interleaved ones missed is a different result from the reverse, even when the count is identical — and it tells you what to look at next time.
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The mean time
Seconds per series you solved. Wrong answers are left out on purpose: a fast wrong answer is a fast wrong answer, and folding it in would make giving up quickly look like fluency.
The verdict word under your score is a rough banding of the count and nothing more — the cuts are at 11, 8 and 5 solved. It exists so the number has a sentence attached to it, not because four bands are a finding. Two runs half an hour apart will often land in different bands, which is itself the most useful thing this page can tell you about how much a single run is worth.
What this version cannot tell you
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12 series is short
Long enough to meet all five rules and get a feel for which ones you spot, not long enough to be a measurement. A run where one lucky guess lands is a run that reads two points higher than it should.
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Multiple choice does some of the work
With 4 numbers in front of you, a rule can be confirmed by testing candidates instead of computing the answer. The same series with a blank box to fill in is a harder task, and the two are not comparable.
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Your conditions are in the result
A tab in the background, a phone that buzzed, the end of a long day — all of it lands in the time and some of it in the count. Compare your own runs on the same evening rather than your run to anyone else’s.
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It is not a diagnosis or a score
Number series appear inside professionally administered batteries, always beside other item types and read by someone qualified. One format on one page is not that, and nothing here turns your count into a score of any kind.
Questions about the number series test
Does it show the answers and explain them?
Yes, and that is the point of this page. Every one of the 12 series is explained the moment you answer it — right or wrong — with the rule stated in that series' own numbers, not a general description of the format. When the run ends, the whole thing is listed under the card: each series as you saw it, the option you picked, the correct answer, and the rule that produced the sequence, with how to spot it next time.
Do I need an account?
No. The number series are generated in your browser and scored there too — nothing is uploaded, nothing is stored, and the result is gone when you close the tab. There is no email box anywhere on this page.
Is this an IQ test?
No. It is one item format — the same number-series format that appears on reasoning and IQ tests — and it reports only what it actually measured: how many of the 12 series you solved, how long you took, and which rules gave you trouble. It does not estimate an IQ, and no single-format test in a browser tab honestly could.
What counts as a good score?
We publish no norms for our version of the number series test, and anyone quoting a number for a browser test is guessing. Two things are worth knowing. 4 options mean about 3 of the 12 come from chance alone. And only 8 series in a run use the three easier rules, so anything above 8 means at least one interleaved or sum-of-two series came apart for you. Beyond that, the comparison worth making is with your own earlier runs.
Do the series repeat if I take it again?
The numbers do not — every run is generated from the clock, so you get 12 fresh series. What stays the same is the recipe: the same five rules, the same mix of 12, and roughly the same easy-to-hard order (neighboring series may swap), which is what makes two of your runs worth comparing.
How do you solve a number series question?
Work through the same short list every time, in order, and most series fall over on the second or third step. Take the gaps between neighboring terms first: if they are all the same, the rule is a fixed step. If the gaps grow, take the gaps between the gaps — a second layer of regularity is the most common way a series hides. If the numbers grow faster than any addition could manage, try dividing one term by the one before it. If none of that works, try adding each pair of neighbors and see whether the sum is the next term. And if the series still refuses, stop reading it as one line and read every other term instead, because two progressions taking turns look like chaos until you split them. Those five checks are the five rules a run is built from, and the worked examples above show each of them with its rule spelled out.
Can you get better at number series?
At number series, yes, and quickly — most of the improvement is learning to check the second differences and to read every other term before deciding a series is irregular. Whether that transfers to reasoning in general is genuinely debated among researchers, and we would rather say so than sell you a promise.
Twelve series is a snapshot. The trend is the point.
In NEURA, number series are one task type inside a daily session of 20, picked for you each morning and pushed toward whatever you keep missing — and after three sessions the Focus Index opens, one score with a 14-day trend behind it. That is the part a single page cannot do.
