Roman numerals
13 symbols: the 7 letters (I, V, X, L, C, D, M) and the 6 standard subtraction pairs (IV, IX, XL, XC, CD, CM), in order of value. With these 13 you can write any number from 1 to 3,999.
Roman numerals still turn up on clocks, in book chapters, after kings' and queens' names, on cornerstones and in the credits of old films. Thirteen symbols are all you need to read and write them.
Learn the seven letters first as one chunk, with a first-letter sentence for the order: I Value Xylophones Like Cows Dig Milk (1, 5, 10, 50, 100, 500, 1,000). Notice the pattern: each step is times 5, then times 2 (1, 5, 10, 50, 100, 500, 1,000). Then learn the six pairs, which follow one rule: a smaller letter before a bigger one is subtracted, and only I, X and C are used that way, each before the next two letters up (IV and IX, XL and XC, CD and CM). To write a number, take the biggest symbol that fits, write it, subtract, and repeat: 2026 is M M (2,000), X X (20), V I (6), so MMXXVI. Practice on dates and clock faces, and come back on day 1, 3, 7 and 21.
Encode make it vivid → Space bring it back on day 1, 3, 7, 21 → Retrieve pull it from your head. From the infographic Remember It on Purpose.
Roman numerals
| Numeral | Value |
|---|---|
| I | 1 |
| IV | 4 |
| V | 5 |
| IX | 9 |
| X | 10 |
| XL | 40 |
| L | 50 |
| XC | 90 |
| C | 100 |
| CD | 400 |
| D | 500 |
| CM | 900 |
| M | 1000 |
Learn the seven letters first as one chunk, with a first-letter sentence for the order: I Value Xylophones Like Cows Dig Milk (1, 5, 10, 50, 100, 500, 1,000). Notice the pattern: each step is times 5, then times 2 (1, 5, 10, 50, 100, 500, 1,000). Then learn the six pairs, which follow one rule: a smaller letter before a bigger one is subtracted, and only I, X and C are used that way, each before the next two letters up (IV and IX, XL and XC, CD and CM). To write a number, take the biggest symbol that fits, write it, subtract, and repeat: 2026 is M M (2,000), X X (20), V I (6), so MMXXVI. Practice on dates and clock faces, and come back on day 1, 3, 7 and 21. · teddyrookbook.com/memory/challenges/roman-numerals/
Sources
Checked October 31, 2026. Progress is kept on this device only (per learner). More lists: all memory challenges · memory games.