Roman Numeral Converter
Type a number or a Roman numeral and the other field converts as you type.
Processed on your device — nothing is sent anywhere.
How it works
- Enter a number from 1 to 3999 in the number field to see its Roman numeral.
- Or enter a Roman numeral such as MCMXCIV to see its numeric value.
- Copy either result with the copy button next to the fields.
Frequently asked questions
- Why is the range limited to 1 to 3999?
- Standard Roman numerals repeat a symbol at most three times, so the largest writable number is MMMCMXCIX, which is 3999. Larger values historically used an overline to multiply by 1000, but that notation is not part of the standard seven-symbol system used today.
- What counts as a valid Roman numeral?
- Only the symbols I, V, X, L, C, D and M are allowed, and they must follow the standard subtractive rules. For example IV is valid for 4, but IIII, VX or IC are rejected because they break the ordering and repetition rules.
- How do I write the year 2026 in Roman numerals?
- 2026 is MMXXVI: MM for 2000, XX for 20, and VI for 6. The converter builds every numeral the same way, taking the largest symbol values first and working down. Other common years are 1999 (MCMXCIX), 2000 (MM), and 2024 (MMXXIV).
- Why is 4 written as IV and not IIII?
- Standard notation uses subtraction: placing I before V means 5 minus 1. This keeps numerals short and unambiguous, which is why 9 is IX and 40 is XL. The main exception you will still see is IIII on some clock faces, a traditional design choice rather than standard notation.
- Is my input sent to a server?
- No. The conversion is a small calculation that runs completely in your browser using JavaScript. Nothing you type is transmitted or stored anywhere, and the converter keeps working even if you go offline after the page has loaded.
About this tool
This Roman numeral converter translates in both directions: type an ordinary number and it produces the Roman numeral, or type a numeral such as MCMLXXXIV and it returns the value 1984. Both fields stay in sync as you type, so there is no convert button to press and no page reload. The supported range is 1 to 3999, which covers everything the standard seven-symbol system (I, V, X, L, C, D, M) can express.
The conversion runs entirely in your browser as a small piece of JavaScript. When you enter a number, the algorithm repeatedly subtracts the largest symbol value that fits — 1000 for M, 900 for CM, 500 for D, and so on — appending symbols until nothing remains. Reading a numeral works in reverse, adding each symbol’s value and subtracting when a smaller symbol precedes a larger one. Because no server is involved, nothing you type is transmitted or logged, and the tool works offline once loaded.
People reach for Roman numerals more often than you might expect: dating a tattoo or engraving, numbering book chapters and movie sequels, writing copyright years for film credits, labeling outlines and legal documents, or checking a child’s homework. The converter is also a quick validator — if you paste a numeral that breaks the rules, such as IIII or IC, it tells you instead of guessing at a value.
A few practical tips: for dates, convert each part separately (day, month, year) since Roman numerals have no digit grouping — 12·IV·MMXXVI is a common tattoo format for 12 April 2026. Remember that there is no zero and no negative numbers in the system. And if you need a number above 3999, the historical convention was a bar over a symbol to multiply it by 1000, but that vinculum notation is rarely used or understood today.