The Fast Count wiki
Mental math: how to calculate faster in your head
Mental math means working out a sum in your head, with no paper and no calculator. Speed does not come from replaying the written method you learned at school: it comes from taking the shortest route the numbers allow. 52 minus 38 is easier if you count up from 38 to 52 than if you take away the units and then the tens.
Fast Count, Neurostim's mental math game, runs through fifteen calculations whose answer is always a number from 1 to 16, picked from a grid. Every day, everyone gets the same set. Here are its rules, its controls, a method for each operation and what its generator really draws, measured over 60,000 calculations.
In short
- Genre: solo mental math against the clock, with the answer picked from a grid.
- Goal: as many right answers as possible out of fifteen, then the shortest time.
- Operations: addition, subtraction, division and "divided then multiplied", in equal shares.
- Answers: always a whole number from 1 to 16.
- Time: 8 seconds per calculation in the daily challenge and the free run; in training, from 3 seconds to no limit, depending on your level.
- Daily challenge: the same fifteen calculations for everyone, renewed at midnight, Paris time. Only your first try is ranked.
- Account: not needed, your first game gives you a guest name.
- Devices: a mouse or keyboard on a computer, a finger on a phone or tablet.
The rules of Fast Count
The four kinds of calculation
Each page asks one question, written out in words: "What is 27 minus 13?".
- Addition: two terms of at least 1, never more than 16 in total, such as 7 plus 8.
- Subtraction: the second term runs from 1 to 40 and the answer from 1 to 16, such as 52 minus 38.
- Division: it always comes out exactly, on a number no higher than 40, such as 39 divided by 3.
- Divided then multiplied: the division first, always exact, then the multiplication, with numbers no higher than 30, such as 18 divided by 6 and multiplied by 5.
The answer grid
You answer by picking the result from sixteen squares, laid out from 1 to 16, four to a row. On the game's own pages, that order never changes.
One answer, and no feedback
An answer cannot be changed, and the game does not tell you whether it was right until the end; only a room tells you after each answer. When the time for a calculation runs out, the page moves on and that calculation counts as missed. An answer that arrives too late counts as wrong.
Two ways of scoring
The time of a game is the sum of the time spent on each calculation, capped at its limit. The server measures it from sending the calculation to receiving your answer, network included.
- Daily challenge and free run: right answers come first, and time only breaks ties.
- Training: score = 1,000 × right answers ÷ seconds, and 0 with no right answer.
These two rules reward different things. Fifteen right in 60 seconds is worth 250 points in training, thirteen right in 40 seconds is worth 325. On the daily leaderboard it goes the other way: 15/15 beats 13/15, whatever the time.
Levels
| Level | Time per calculation |
|---|---|
| 1 | no limit |
| 2 | 8 seconds, as in the daily challenge |
| 3 | 5 seconds |
| 4 | 3 seconds |
Everyone starts at level 1. Moving up takes 14 right answers out of 15, in training and at your current level. That level is shared with the other training games marked out of 20: Patrons, Memo Chars, Counter and Color keypad. On Fast Count you can always pick a lower level, but it will not move you up.
Working it out in your head, one operation at a time
Small problems get faster answers than large ones: psychologists call this the problem-size effect. So the whole method comes down to one idea: shrink the numbers before you calculate.
Learn the grid
Your hand should find the answer without your eyes hunting for it. The grid reads like the 4 times table: the last column holds the multiples of 4, and the rows begin with 1, 5, 9 and 13.
14 comes right after 13: fourth row, second column.
Addition: go through ten
Fast Count's additions stay small, and only one in four crosses a ten. For those, make a ten first: 7 plus 8 is 7 plus 3, then 5 more, so 15. Learn the doubles by heart: 8 plus 8 is 16, so 7 plus 8 is one less.
Subtraction: count up
The numbers look big, but the gap between them stays small. The answer is never above 16, so the two terms are always close. Do not take away: start from the smaller number and climb to the larger one.
For 52 minus 38: from 38 to 40 is 2, from 40 to 52 is 12, so the answer is 14. A 2010 study found that adults switch to this method by themselves when the number being subtracted is clearly larger than the answer. Here, it is larger in four subtractions out of five.
Division: look at the divisor
Read the divisor first, because it tells you a lot about the answer:
- By 1: the answer is the number itself.
- Above 20: the answer has to be 1, since the starting number is no higher than 40.
- From 14 to 20: the answer is 1 or 2, for the same reason.
- By 2, 3 or 4: split the number into easy pieces. For 39 divided by 3, 30 gives 10 and 9 gives 3, so 13.
Divided then multiplied: look for the shortcut
This calculation looks the longest and often hides the shortest route. Since the final answer is no higher than 16, the multiplication stays tiny. Look at the numbers before you calculate:
- The same number twice: 17 divided by 17 and multiplied by 9 gives 9. The answer is the last number.
- Multiplied by 1: only the division matters.
- Divided by 1: only the multiplication matters.
- Otherwise: two steps, in order. 18 divided by 6 is 3, and 3 times 5 is 15.
Getting faster
- Read to the end of the sentence. "18 divided by 6" may carry on with "and multiplied by 5". Stopping at 3 gives a wrong answer that nothing flags until the game is over.
- Play for your mark in the challenge, for your speed in training. On the daily leaderboard, 15/15 in 1 min 50 beats 14/15 in 20 seconds. A mistake costs more there than any amount of hesitation.
- Do not let a calculation run out. With no answer, you lose both the 8 seconds and the point. A likely answer at least stops the clock.
- On a keyboard, type the number rather than moving to it. An answer takes 2.44 key presses on average with the digits, against 4.05 with the arrows.
- Warm up with no limit. Level 1 shows you where you really get stuck. Only cut the time once your answers stay right.
- Go back to the operation that costs you. The mistake list in training soon shows whether subtractions or the two-step sums are holding you back.
- Look after your connection. The network trip is part of your time, and each calculation loads a new page.
Once exact sums come easily, change the exercise: Swarmcount works on estimating by eye, Cagewise on the logic of arithmetic cages, and Numerank puts mental math to work in a battle of numbers.
Benchmarks: what the generator really draws
The mix of calculations
We drew 4,000 games, or 60,000 calculations, with the game's generator in November 2026.
| Calculation | Share | Largest number seen | What to know |
|---|---|---|---|
| Addition | 25% | 15 | one in four (25.1%) crosses a ten |
| Subtraction | 25% | 56 | 79.6% have a second term larger than the answer, 40.7% need borrowing if you write them out |
| Division | 25% | 40 | 24.1% are by 1, 53.2% come straight from the tables up to 10 |
| Divided then multiplied | 25% | 30 | only 31.7% need two real steps |
The last kind deserves a closer look: the same number appears twice in 37.7% of cases, the multiplier is 1 in 32.9%, the divisor is 1 in 12.2%. The division in the middle gives 1, 2 or 3 in 73% of cases. For all its length, this calculation often comes down to a single step, as long as you spot the shortcut.
No two games are quite alike
Each calculation's kind is drawn separately: a game holds three or four of each on average, but 5.3% of games have none of one kind, and some reach eleven calculations of the same kind. A daily challenge heavy on subtraction can happen, and when it does, it happens to everyone.
The answers
Answers are spread almost evenly: from 6.1% to 6.6% for each number from 2 to 16. The 1 is rarer (4.6%), because an addition cannot produce it. The same answer comes up twice in a row in 6.2% of cases, so clicking the same square twice does not have to mean a mistake.
World records, a long way from here
There is no single mental math record, because each event has its own. At the 2024 Mental Calculation World Cup, Aaryan Nitin Shukla added ten 10-digit numbers in an average of 7.808 seconds over ten questions, a world record according to Wikipedia (checked on 7 November 2026). In Japan, in the flash anzan event of the soroban championship, Takeo Sasano added fifteen three-digit numbers in 1.7 seconds. These feats do not compare with Fast Count: to see where you stand, look at today's times instead.
What about your brain?
Calculating mostly teaches you to calculate better. A 2016 review examined the studies cited by brain-training companies: the evidence is strong for the trained task, weaker for closely related tasks and scarce for everyday life. A 2010 study of 11,430 participants over six weeks found no transfer to untrained tasks. So Fast Count promises nothing for your memory or your IQ.
The history of mental calculation
- 1867-1950: Jacques Inaudi, a child from Piedmont who said he practised while minding sheep, becomes a "calculating prodigy" of the stage, from the Robert-Houdin theatre in Paris to the fairgrounds. He performs before the French Academy of Sciences in 1892-1893, and Alfred Binet devotes a study to him. He could give the day of the week for a date in under two seconds.
- 1998: the Mind Sports Olympiad begins its annual world championships in mental calculation.
- 2004: the first Mental Calculation World Cup brings together 17 participants from 10 countries in Annaberg-Buchholz, Germany, on 30 October. It is held every two years, with addition, multiplication, square root and calendar events.
- 2005: Nintendo releases Brain Age in Japan on 19 May, inspired by the work of neuroscientist Ryuta Kawashima. One of its exercises runs through twenty simple sums: additions, subtractions and multiplications.
- 2016: a controlled trial published that year followed 204 children for three years, some of them taught the mental abacus. Those pupils calculated better than the control group, with no gain in basic abilities such as working memory.
Fast Count comes from the first Neurostim, online since 2008: a training game to which the 2026 redesign added the daily challenge and its leaderboards.
Frequently asked questions
How do you do mental math faster?
To do mental math faster, take the shortest route the numbers allow instead of replaying the written method: go through ten to add, count up to subtract, and spot a number divided by itself. Then play short games and read back through your mistakes.
How do you get better at mental math as an adult?
Find the operation that costs you the most mistakes, then work on it at a pace where you stay accurate before cutting the time. Fast Count's training lists each mistake with the right answer and opens a faster level once you reach 14 out of 15.
What are the best mental math tricks for division?
The best trick for division is to split the number into pieces the divisor shares easily: 39 divided by 3 is 30 divided by 3 plus 9 divided by 3, so 13. On Fast Count every division comes out exactly, and a divisor above 20 always gives 1.
Is mental math good for your brain?
Mental math clearly makes you better at mental math, but the evidence for wider benefits is weak. A 2016 review found strong evidence for trained tasks and little for everyday cognition, and a 2010 study of 11,430 people found no transfer to untrained tasks.
Is mental math a sign of intelligence?
Not on its own: fast calculation is largely a trained skill. Jacques Inaudi, the famous stage calculator, was judged intelligent, but the doctors who examined him put his gift down to a specialised, trained memory, and he struggled to memorise a fable.
Is mental math a skill you can learn?
Yes, mental math is a skill that responds to practice, since training reliably improves the task being trained. In a three-year controlled trial with 204 children aged 5 to 7, those taught the mental abacus in ordinary classrooms outperformed the control group on arithmetic.
What is the mental math world record?
There is no single mental math world record, because each event has its own. At the 2024 Mental Calculation World Cup, Aaryan Nitin Shukla added ten 10-digit numbers in an average of 7.808 seconds over ten questions, according to his Wikipedia page, checked in November 2026.
Are mental math and the abacus the same thing?
No: the mental abacus is one method of mental math, in which you picture an abacus and move its beads in your head, with no physical abacus at all. It is used in countries including Japan, China and South Korea. Other methods rely on number facts and shortcuts.
What is a good mental math game for adults?
Fast Count is a free mental math game for adults that needs no account: no school levels, fifteen sums against the clock, a shared daily challenge and a leaderboard. Answers never go above 16, so the difficulty comes from speed rather than from big numbers.
Is there a free mental math test online?
Fast Count works as a free personal test of mental math, because it measures your speed and accuracy over fifteen calculations. It is neither a standardised aptitude test nor a medical examination: the score only compares you with yourself and with other players.
Sources
- Wikipedia, Mental calculation, Mental Calculation World Cup, Aaryan Nitin Shukla, Mental abacus and Brain Age, checked on 7 November 2026.
- Wikipedia (French), Jacques Inaudi, checked on 7 November 2026.
- Thomas J. Faulkenberry, A Single-Boundary Accumulator Model of Response Times in an Addition Verification Task, Frontiers in Psychology, 2017, for the problem-size effect.
- Peters, De Smedt, Torbeyns, Ghesquière and Verschaffel, Adults' use of subtraction by addition, Acta Psychologica 135 (3), 2010, pp. 323-329.
- Simons et al., Do "Brain-Training" Programs Work?, Psychological Science in the Public Interest 17 (3), 2016, pp. 103-186.
- Owen et al., Putting brain training to the test, Nature 465, 2010, pp. 775-778.
- Barner et al., Learning Mathematics in a Visuospatial Format, Child Development 87 (4), 2016, pp. 1146-1158.
Your turn
Today's Fast Count challenge is the same for everyone until midnight, Paris time. No account needed: you get a guest name with your first game.
Games of the same kind
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