Roman Numeral Converter — Encode & Decode Roman Numerals
Roman Numeral Reference
| Roman Numeral | Value | Notes |
|---|---|---|
| I | 1 | Basic symbol |
| V | 5 | Basic symbol |
| X | 10 | Basic symbol |
| L | 50 | Basic symbol |
| C | 100 | Basic symbol |
| D | 500 | Basic symbol |
| M | 1000 | Basic symbol |
| IV | 4 | Subtractive notation |
| IX | 9 | Subtractive notation |
| XL | 40 | Subtractive notation |
| XC | 90 | Subtractive notation |
| CD | 400 | Subtractive notation |
| CM | 900 | Subtractive notation |
Key Rules: Subtractive notation is used when a smaller numeral appears before a larger one. Only I, X, and C can be used as subtractive numerals, and only before the next two higher values (I before V or X, X before L or C, C before D or M).
Frequently Asked Questions
What is the largest number that can be represented in Roman numerals?
The largest number typically representable in standard Roman numerals is 3,999 (MMMCMXCIX). This limitation exists because there's no standard symbol for numbers 4,000 and above in classical Roman numeral notation.
Why do Roman numerals use subtractive notation like IV for 4?
Subtractive notation was developed to avoid writing four consecutive identical symbols, making numbers more compact and easier to read. For example, IV (4) is simpler than IIII, and CD (400) is cleaner than CCCC.
What are the most common mistakes when writing Roman numerals?
Common errors include using subtractive notation incorrectly (like writing IC for 99 instead of XCIX), repeating symbols more than three times consecutively, and placing smaller numerals before larger ones inappropriately.
Where are Roman numerals still used today?
Roman numerals are commonly used for clock faces, movie copyright dates, book chapters, sporting events (like Super Bowl LVII), formal documents, and architectural inscriptions. They're also used in outlines and to denote monarchs and popes.