How to use Roman Numeral Converter
The Roman numeral converter converts instantly in both directions: type an Arabic number (1–3,999,999) to get its Roman numeral, or type a Roman numeral to get the Arabic value. The tool also shows a symbol-by-symbol breakdown so you can see exactly how each numeral contributes to the total. For numbers above 3,999, parenthesis notation is used to represent thousands-multiples (e.g. (IV) = 4,000), consistent with the extended vinculum convention.
- Type a number (e.g. 2024) or a Roman numeral (e.g. MCMXCIV) in the input box.
- The tool auto-detects whether you entered a number or a Roman numeral.
- Click Convert (or press Enter) to see the result.
- Expand the Symbol Breakdown table to see the value of each numeral token.
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Roman numeral rules and subtractive notation
Roman numerals are formed by combining seven base symbols and applying two rules. Additive rule: identical or smaller symbols placed after a larger one are added (VI = 6, XV = 15). Subtractive rule: a smaller symbol placed immediately before a larger one is subtracted (IV = 4, IX = 9, XL = 40, XC = 90, CD = 400, CM = 900). Only these six subtractive pairs are valid; writing IIX for 8 or VL for 45 is not standard. A symbol may not be repeated more than three times consecutively (so 4 must be IV, not IIII).
| Symbol | Value | Notes |
|---|---|---|
| I | 1 | Can be repeated up to 3 times |
| V | 5 | Cannot be repeated |
| X | 10 | Can be repeated up to 3 times |
| L | 50 | Cannot be repeated |
| C | 100 | Can be repeated up to 3 times |
| D | 500 | Cannot be repeated |
| M | 1,000 | Can be repeated up to 3 times (standard); parentheses for thousands above |
Extended Roman numerals beyond 3,999
The standard Roman system tops out at 3,999 (MMMCMXCIX). To represent larger numbers, the historical vinculum convention placed a bar (overline) above a numeral to multiply it by 1,000. This tool uses parentheses as a typographically safe equivalent: (V) = 5,000; (X) = 10,000; (L) = 50,000; (C) = 100,000; (D) = 500,000; (M) = 1,000,000. Combined with a suffix: (III)DCCCXCIX = 3,899 in thousands, i.e. 3,899,000. Roman numerals above 3,999 appear in historical contexts such as clock faces, book volumes, and film copyright notices.
Play the Roman Numeral Speed Quiz with friends
This converter also powers a Roman Numeral Speed Quiz you can challenge friends to. Hit "Play with friends", create a room, and share the code — everyone converts the same seeded set of numbers, and the player with the most correct answers (fastest as a tiebreaker) tops the leaderboard. The shared seed means every player faces the identical questions, so it is a fair test of who really knows their I, V, X, L, C, D and M. It is a free, browser-based learning game that works great in classrooms or as a quick brain teaser with friends. No sign-up needed. Browse all the quiz games on the multiplayer games hub.
Worked examples
Number to Roman
Inputs: 2025
Result: MMXXV
Roman to number
Inputs: MCMXCIV
Result: 1994
Subtractive pairs
Inputs: 49
Result: XLIX
Common numbers in Roman numerals
| Number | Roman numeral |
|---|---|
| 4 | IV |
| 9 | IX |
| 40 | XL |
| 90 | XC |
| 400 | CD |
| 900 | CM |
| 2025 | MMXXV |
Glossary
- Subtractive notation
- Placing a smaller numeral before a larger one to indicate subtraction (e.g. IV = 4, CM = 900).
- Additive notation
- Placing numerals of equal or decreasing value together to indicate addition (e.g. VI = 6).
- Vinculum
- A horizontal bar over a Roman numeral that multiplies its value by 1,000, used for numbers above 3,999.
- ASCII-safe notation
- Using parentheses around a Roman numeral to represent the vinculum in text: (V) = 5,000.
Related reading
Frequently Asked Questions
Why use Roman Numeral Converter?
- Converts in both directions — Arabic integer to Roman numeral and Roman to Arabic — instantly
- Shows a symbol-by-symbol token breakdown explaining exactly how each numeral builds the value
- Supports extended vinculum parenthesis notation for numbers beyond the standard 3,999 limit
- Auto-detects whether you entered a digit or letter string so no mode switching is needed
Common use cases
- Decode the Roman numeral copyright year at the end of a film or television programme
- Convert a chapter or section number into Roman numerals for book or thesis formatting
- Verify the year engraved on a building cornerstone or historical monument plaque
- Find the Arabic equivalent of a Roman-numeral clock face position for a design project
- Generate the Roman numeral for a Super Bowl edition or modern Olympiad number
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