Roman Numerals Explained: How to Read and Write Them
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Roman numerals use seven letters: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500 and M = 1000. Symbols are added from largest to smallest, except that a smaller symbol placed before a larger one is subtracted, so IV = 4 and CM = 900.
The symbols
| I | V | X | L | C | D | M |
|---|---|---|---|---|---|---|
| 1 | 5 | 10 | 50 | 100 | 500 | 1000 |
The subtraction pairs
Only six are allowed:
| IV | IX | XL | XC | CD | CM |
|---|---|---|---|---|---|
| 4 | 9 | 40 | 90 | 400 | 900 |
Writing a number
Break it into thousands, hundreds, tens and units, and write each part.
2026: = MM + XX + VI = MMXXVI.
49: = XL + IX = XLIX (not IL, which is not a valid pair).
Reading a numeral
MCMXCIV: M (1000) + CM (900) + XC (90) + IV (4) = 1994.
Limits
Standard numerals go up to 3999 (MMMCMXCIX). There is no symbol for zero, which is one reason the system is no longer used for arithmetic.
Common mistakes
- Writing IIII instead of IV (clock faces are an exception).
- Inventing pairs like IL for 49 or VX for 5.
- Repeating V, L or D, which are never repeated.
Practice questions
- Write 14 in Roman numerals.
- What is CDXLIV?
- Write 1999.
Answers: 1) XIV 2) 444 3) MCMXCIX
Convert any number from 1 to 3999 with the Roman numeral converter. For other number systems, try the binary and hex converter and read binary and hexadecimal explained.
Frequently asked questions
How do you write 0 in Roman numerals?
You cannot. The Roman system had no symbol for zero.
Why do clocks show IIII?
It is a design tradition; IV is the standard form.
How are numbers above 3999 written?
Historically a bar over a numeral multiplied it by 1000, but this is rarely used today.
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