在『阿拉伯』數字傳入歐洲時,其數字為古『羅馬』數字. 今用於鐘錶日曆,但『羅馬』數字冇『0』
『羅馬』數字四規
- 倍數重複
- 三倍限制
- 右加左減
- 加綫乘千
| 『羅馬』數字 | 記數規則 | 解話 |
| Ⅰ | 1 | 表示1 |
| Ⅱ | 1+1=2 | 兩個Ⅰ |
| Ⅲ | 1+1+1=3 | 三個Ⅰ |
| Ⅳ | -1+5=4 | Ⅴ左則Ⅰ |
| Ⅴ | 5 | Ⅴ表示5 |
| Ⅵ | 5+1=6 | Ⅴ右則Ⅰ |
| Ⅶ | 5+1+1=7 | Ⅴ右則兩個Ⅰ |
| Ⅷ | 5+1+1+1=8 | Ⅴ右則三個Ⅰ |
| Ⅸ | -1+10=12 | Ⅹ左則Ⅰ |
| Ⅹ | 10 | Ⅹ表示10 |
| Ⅺ | 10+1=11 | Ⅹ右則Ⅰ |
| Ⅻ | 10+1+1=12 | Ⅹ右則兩個Ⅰ |
| 『阿拉伯』數字 | 『古羅馬』數字 | WORD便捷鍵 |
| 1 | Ⅰ | ALT+8544 |
| 2 | Ⅱ | ALT+8545 |
| 3 | Ⅲ | ALT+8546 |
| 4 | Ⅳ | ALT+8547 |
| 5 | Ⅴ | ALT+8548 |
| 6 | Ⅵ | ALT+8549 |
| 7 | Ⅶ | ALT+8550 |
| 8 | Ⅷ | ALT+8551 |
| 9 | Ⅸ | ALT+8552 |
| 10 | Ⅹ | ALT+8553 |
| 11 | Ⅺ | ALT+8554 |
| 12 | Ⅻ | ALT+8555 |
| 13 | XIII | |
| 14 | XIV | |
| 15 | XV | |
| 16 | XVI | |
| 17 | XVII | |
| 18 | XVIII | |
| 19 | XIX | |
| 20 | XX | |
| 21 | XXI | |
| 30 | XXX | |
| 40 | XL | |
| 50 | L | ALT+8556 |
| 60 | LX | |
| 70 | LXX | |
| 80 | LXXX | |
| 90 | XC | |
| 100 | C | ALT+8557 |
| 200 | CC | |
| 300 | CCC | |
| 400 | CD | |
| 500 | D | ALT+8558 |
| 600 | DC | |
| 700 | DCC | |
| 800 | DCCC | |
| 900 | CM/DCCCC | |
| 1,000 | M | ALT+8559 |
| 2,000 | MM | |
| 3,000 | MMM | |
| 4,000 | MV | |
| 5,000 | V | |
| 10,000 | X | |
| 50,000 | L | |
| 100,000 | C | |
| 500,000 | D | |
| 1,000,000 | M |