Roman Numeral Converter
Free Roman numeral converter that goes both ways - numbers to Roman and Roman to numbers. Includes step-by-step breakdowns and a reference table.
About Roman Numeral Converter
This Roman numeral converter provides instant, bidirectional conversion between standard numbers (1-3999) and Roman numerals. It handles decoding inscriptions, formatting dates, and any other Roman numeral task with a clear step-by-step breakdown.
Two Conversion Modes
Switch between Number to Roman and Roman to Number modes using the tab selector. In number mode, type any integer from 1 to 3999 and see the Roman numeral equivalent instantly. In Roman mode, enter a Roman numeral string and get the decimal value.
Step-by-Step Breakdown
Every conversion displays a detailed breakdown showing how the result is constructed. For number-to-Roman conversions, you see each component (e.g., 1994 = M + CM + XC + IV). This makes the tool useful for learning Roman numeral rules, not just converting.
Input Validation
The converter checks your input in real time and provides clear error messages for invalid entries. It detects out-of-range numbers, unrecognized characters, and improper Roman numeral sequences, so you can be confident the result is correct.
Reference Table
A built-in reference table shows common Roman numeral values from I to M, including the subtractive forms (IV, IX, XL, XC, CD, CM). Use it as a quick cheat sheet while working with Roman numerals in any context.
Common Uses
- Decoding dates on buildings, monuments, and movie credits
- Formatting outline headings and list items in academic papers
- Studying or teaching Roman numeral notation
- Converting Super Bowl numbers and other event designations
For other number format conversions, try the number to words converter or the binary to decimal converter. All conversions happen instantly in your browser.
Frequently Asked Questions
What is the valid range for Roman numerals?
Standard Roman numerals represent values from 1 to 3999. There is no Roman numeral for zero, and values above 3999 traditionally require a vinculum (overline notation) which is not part of the standard system. This converter supports the full 1-3999 range.
How does subtractive notation work in Roman numerals?
Subtractive notation places a smaller value before a larger one to indicate subtraction. For example, IV is 4 (5 minus 1), IX is 9, XL is 40, XC is 90, CD is 400, and CM is 900. This avoids repeating a symbol four times in a row.
What does the step-by-step breakdown show?
When converting a number to Roman numerals, the breakdown shows how the number is decomposed into its Roman components. For example, 1994 is broken into M (1000) + CM (900) + XC (90) + IV (4), making it easy to understand how the final result MCMXCIV is constructed.
How are invalid Roman numeral inputs handled?
The converter validates your input in real time. It checks for invalid characters, illegal sequences (like IIII or VV), and out-of-range values. If the input is invalid, a clear error message explains what went wrong so you can correct it.