What are Roman numerals?
Roman numerals are the number system of ancient Rome, still seen today on clock faces, in book chapters, on monuments and in copyright dates. Instead of digits, they use seven letters whose values are added together — with a clever subtraction trick to keep numbers short. This converter turns any whole number from 1 to 3999 into its Roman numeral and back, instantly and with the working shown.
The seven symbols
Every Roman numeral is built from these letters:
| Symbol | Value |
|---|---|
| I | 1 |
| V | 5 |
| X | 10 |
| L | 50 |
| C | 100 |
| D | 500 |
| M | 1,000 |
The subtractive rule
To avoid writing four identical symbols in a row, a smaller symbol placed before a larger one is subtracted. So 4 is IV (5 − 1), 9 is IX (10 − 1), 40 is XL, 90 is XC, 400 is CD and 900 is CM. Symbols are otherwise written largest to smallest and added up.
Reference chart
Common values, generated by the same engine that powers the converter.
| Number | Roman numeral |
|---|---|
| 1 | I |
| 2 | II |
| 3 | III |
| 4 | IV |
| 5 | V |
| 6 | VI |
| 7 | VII |
| 8 | VIII |
| 9 | IX |
| 10 | X |
| 20 | XX |
| 30 | XXX |
| 40 | XL |
| 50 | L |
| 90 | XC |
| 100 | C |
| 400 | CD |
| 500 | D |
| 900 | CM |
| 1,000 | M |
Worked example: 1994 → MCMXCIV
1994 is built from M (1000), CM (900), XC (90) and IV (4).
| Symbol | Value |
|---|---|
| M | 1,000 |
| CM | 900 |
| XC | 90 |
| IV | 4 |
| MCMXCIV | 1,994 |
Frequently asked questions
What are Roman numerals?+
A number system from ancient Rome using letters — I, V, X, L, C, D and M — to represent 1, 5, 10, 50, 100, 500 and 1000. Numbers are built by combining these symbols.
How do you write a number in Roman numerals?+
Write the symbols from largest to smallest and add their values, using the subtractive pairs for 4s and 9s. For example 2024 = MM (2000) + XX (20) + IV (4) = MMXXIV.
What is the subtractive rule?+
When a smaller symbol comes before a larger one, it is subtracted: IV = 4, IX = 9, XL = 40, XC = 90, CD = 400 and CM = 900. This avoids writing four of the same symbol in a row.
What is the largest number in Roman numerals?+
Using standard letters, the largest is 3999 (MMMCMXCIX). Larger numbers historically used a bar (vinculum) over a symbol to multiply it by 1000, which this converter does not use.
Is there a Roman numeral for zero?+
No. The Roman system has no symbol for zero; it only represents positive whole numbers from 1 upward.
Why is 4 written IV and not IIII?+
Standard modern Roman numerals use the subtractive form IV for 4. (You may still see IIII on some clock faces, a traditional stylistic exception.)
How do you convert a Roman numeral to a number?+
Add each symbol’s value, subtracting any symbol that is smaller than the one after it. MCMXCIV = 1994. This converter does it instantly and checks the numeral is valid.
What does MMXXIV mean?+
MMXXIV is 2024: MM = 2000, XX = 20, IV = 4.
Can a symbol be repeated?+
I, X, C and M can be repeated up to three times in a row (III = 3). V, L and D are never repeated. Anything needing a fourth repeat uses a subtractive pair instead.
Where are Roman numerals still used?+
Clock faces, book chapters, movie sequels and copyright years, the Super Bowl, monarch and pope names, and building cornerstones.
Sources
- Wolfram MathWorld — Roman Numerals
- Encyclopaedia Britannica — Roman numeral
- Math is Fun — Roman Numerals
Formula and data last reviewed by the TheCalculatorVault team on 26 June 2026. Figures are for general information, not professional advice.
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