Roman Numeral Calculator – Convert Roman Numerals to Numbers
Convert between Roman numerals and numbers
Table of Contents
How to Use
- Select conversion type (Roman to Number or Number to Roman)
- Enter the Roman numeral or number you want to convert
- Click calculate to see the conversion result
- View the conversion formula and learn the relationship
What are Roman Numerals?
Roman numerals are a numeral system that originated in ancient Rome and remained the usual way of writing numbers throughout Europe well into the Late Middle Ages. Numbers in this system are represented by combinations of letters from the Latin alphabet.
The standard Roman numerals use the symbols I, V, X, L, C, D, and M representing respectively 1, 5, 10, 50, 100, 500, and 1,000 in the Hindu-Arabic numeral system.
Basic Roman Numeral Symbols
| Symbol | Value | Description |
|---|---|---|
| I | 1 | One (unus) |
| V | 5 | Five (quinque) |
| X | 10 | Ten (decem) |
| L | 50 | Fifty (quinquaginta) |
| C | 100 | One hundred (centum) |
| D | 500 | Five hundred (quingenti) |
| M | 1000 | One thousand (mille) |
Roman Numeral Rules
- When a smaller value appears before a larger value, it is subtracted (IV = 4, IX = 9)
- When a smaller value appears after a larger value, it is added (VI = 6, XI = 11)
- The same symbol cannot be repeated more than three times in succession (III = 3, but not IIII)
- The symbols V, L, and D are never repeated
- The subtractive principle is only used with specific pairs: IV (4), IX (9), XL (40), XC (90), CD (400), CM (900)
Common Examples
| Number | Roman Numeral | Breakdown |
|---|---|---|
| 4 | IV | 5 - 1 |
| 9 | IX | 10 - 1 |
| 14 | XIV | 10 + (5 - 1) |
| 40 | XL | 50 - 10 |
| 44 | XLIV | (50 - 10) + (5 - 1) |
| 99 | XCIX | (100 - 10) + (10 - 1) |
| 400 | CD | 500 - 100 |
| 944 | CMXLIV | (1000 - 100) + (50 - 10) + (5 - 1) |
| 1999 | MCMXCIX | 1000 + (1000 - 100) + (100 - 10) + (10 - 1) |
Frequently Asked Questions
- What is the highest number that can be written in Roman numerals?
- Using standard Roman numeral rules, the highest number is 3,999 (MMMCMXCIX). Larger numbers require special notation with bars over symbols to indicate multiplication by 1,000.
- Why don't Roman numerals have a zero?
- The Roman numeral system developed before the concept of zero was introduced to mathematics. The Romans had no symbol for zero, which is one reason the system was eventually replaced by Arabic numerals.
- Are Roman numerals still used today?
- Yes! Roman numerals are still used for clock faces, book chapters, movie sequels, sporting events (Super Bowl, Olympics), building cornerstones, and formal documents.
- How do you read large Roman numerals?
- Read from left to right, adding values unless a smaller value appears before a larger one, in which case subtract the smaller from the larger. Practice with common numbers like dates (MMXXIV = 2024).