Roman Numeral Converter
Two-way conversion between decimal numbers and Roman numerals
| Roman | Decimal | Roman | Decimal |
|---|---|---|---|
| I | 1 | IV | 4 |
| V | 5 | IX | 9 |
| X | 10 | XL | 40 |
| L | 50 | XC | 90 |
| C | 100 | CD | 400 |
| D | 500 | CM | 900 |
| M | 1000 |
Frequently Asked Questions
What is the range of numbers that can be converted to Roman numerals? +
Standard Roman numerals represent numbers from 1 to 3999. The number 4000 and above would require a bar notation (vinculum) which is not part of the standard system. This converter handles the full standard range of 1 to 3999.
How does the subtractive notation work in Roman numerals? +
Subtractive notation places a smaller value before a larger one to indicate subtraction. For example, IV = 4 (5-1), IX = 9 (10-1), XL = 40 (50-10), XC = 90 (100-10), CD = 400 (500-100), and CM = 900 (1000-100). This avoids repeating a symbol four times.
What are the basic Roman numeral symbols and their values? +
The seven basic Roman numeral symbols are: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, and M = 1000. All Roman numerals are combinations of these seven symbols using additive and subtractive notation.
How do I know if a Roman numeral is valid? +
A valid Roman numeral follows specific rules: symbols I, X, C, M can repeat up to 3 times; V, L, D never repeat; subtractive pairs are limited (IV, IX, XL, XC, CD, CM); and the value generally decreases from left to right except for subtractive pairs. This converter validates your input automatically.
Why can't Roman numerals represent zero? +
The Roman numeral system was developed before the concept of zero was widely adopted in Western mathematics. Romans had no symbol for zero because their numeral system was primarily used for counting and record-keeping, where the concept of "nothing" wasn't needed as a number.