Most people can hold about seven digits in their head before they start losing them. The way past that limit is not to hold more digits; it is to hold fewer, bigger things. Group the digits, say them out loud, and give the groups a meaning, and a sixteen digit number becomes four or five items, which almost anyone can keep. This page walks through five techniques, from the one you can use today to the ones memory competitors rely on, and a short practice plan to go with them.
Take the number memory test Find your starting span, then practise against it.
Why numbers are hard to remember
A digit carries no meaning on its own. A word brings sounds, pictures and associations with it, all of which give your memory something to grip. A 7 followed by a 3 brings nothing. That is why a shopping list of eight items is easy and an eight digit number is not.
Short term memory also has a hard limit on how many separate things it can hold at once. George Miller put it at seven, give or take two, in 1956, and later research by Nelson Cowan suggests the true figure is closer to four when people cannot rehearse. Every technique below works the same way: it reduces how many separate things you are holding, without reducing how many digits you remember.
1. Chunk the digits into groups
This is the single biggest win, and you can use it immediately. Instead of holding 5, 8, 1, 9, 3, 6, 2, 7 as eight items, hold 58, 19, 36, 27 as four. Phone numbers are printed in groups for exactly this reason. Start with pairs, then move to groups of three once pairs feel easy: twelve digits as four triples is well within anyone’s span.
2. Say them out loud
Your brain keeps a short loop of recent sounds running, which psychologists call the phonological loop. Saying the digits aloud, or under your breath, puts them into that loop, where they last noticeably longer than a purely visual memory. Say the groups with a rhythm, the way you would read out a phone number: fifty eight, nineteen, thirty six, twenty seven. The rhythm itself becomes part of the memory.
3. Give the groups a meaning
A group that already means something is stored almost for free. 19 might be an age, 1984 a year, 23 a sports shirt number, 365 the days in a year. The more of a number you can turn into things you already know, the less raw memory it takes.
This is how the most famous case in memory research worked. In a study by Anders Ericsson and William Chase, a student known as S.F. began with an ordinary span of about seven digits. He was a keen runner, and he taught himself to hear groups of digits as running times: 3492 became three minutes 49.2 seconds, a good mile. After more than 230 hours of practice over nearly two years, he could recall around 80 digits. His basic memory never changed; his ability to turn digits into meaning did.
4. Learn the major system
The major system makes step three work for any number, not just the ones that happen to mean something. Each digit becomes a consonant sound, and you add vowels freely to make words.
| Digit | Sound | Remember it by |
|---|---|---|
| 0 | s, z | z is for zero |
| 1 | t, d | t has one downstroke |
| 2 | n | n has two downstrokes |
| 3 | m | m has three |
| 4 | r | the last sound of four |
| 5 | l | L is the Roman numeral 50 |
| 6 | j, sh, ch | a j looks like a backwards 6 |
| 7 | k, hard g | a k is made of two 7s |
| 8 | f, v | a handwritten f looks like an 8 |
| 9 | p, b | p is a mirrored 9 |
With it, 32 is man, 41 is rat, 92 is pen and 85 is file. A number like 3241 9285 becomes a man, a rat, a pen and a file, which you can picture as a little scene. It takes a few weeks of practice before the conversion is quick, but after that no number is meaningless.
5. Use a memory palace for long numbers
For numbers too long to hold as one scene, competitive memorisers use a memory palace, also called the method of loci. Picture a route you know well, such as the walk through your home, and place each image from the major system at a spot along it: the man at the front door, the rat on the sofa, the pen in the kitchen. To recall the number, walk the route in your mind. It is the technique behind the feats you see in memory competitions, and it works for anyone willing to practise it.
A two week practice plan
Ten minutes a day is enough. Take the number memory test a few times at the start to find your baseline, then:
| Days | Focus |
|---|---|
| 1 to 3 | Chunk every number into pairs, out loud |
| 4 to 7 | Move to groups of three, keep saying them |
| 8 to 10 | Notice groups that already mean something: years, ages, numbers you know |
| 11 to 14 | Learn the major system for 0 to 9, then start converting pairs into words |
Use your typical score across a few runs rather than your best single run, because one lucky attempt says little. Most people find chunking alone adds two to four digits within the first week. The Number Memory Test page has a breakdown of what each strategy usually adds, and the chimp test guide covers a very different kind of number memory, where the digits are spread across a screen.
Frequently asked questions
Can you train your memory for numbers?
Yes, and faster than most people expect. Raw span, the number of separate digits you can hold, barely moves with practice. What changes is how many digits you pack into each thing you hold, and that responds to practice within days.
How did someone remember 80 digits?
In a well known study by Anders Ericsson and William Chase, a student known as S.F. practised for about an hour a day. As a keen runner, he learned to turn groups of digits into running times, so a string of digits became a handful of meaningful race times. After more than 230 hours over nearly two years, his digit span went from about 7 to about 80.
What is the major system?
A code that turns each digit into a consonant sound: 1 is t or d, 2 is n, 3 is m, 4 is r, 5 is l, 6 is j, sh or ch, 7 is k or g, 8 is f or v, 9 is p or b, and 0 is s or z. You add vowels freely to make words, so 32 becomes man and 41 becomes rat. Words are far easier to remember than digits.
Is chunking cheating on a memory test?
No. Chunking is how memory works for everyone, and every strong score on a number memory test uses it. A test that forbade grouping would be measuring something nobody does in real life.
How long does it take to improve?
Chunking and saying digits aloud usually add a couple of digits within a few sessions. Giving the chunks meaning, and especially the major system, take a few weeks of short daily practice before they are fast enough to use under a time limit.
Put it into practice Free, no signup, a percentile after every run.