Roman Numeral Converter
Convert any number from 1 to 3999 to Roman numerals — or decode any Roman numeral back to Arabic. Instant results with a symbol-by-symbol breakdown. Free, no account required, nothing leaves your device.
Quick examples
How It Works
Pick a direction
Choose "Arabic → Roman" to convert a number to its Roman numeral, or "Roman → Arabic" to decode a Roman numeral string.
Type your value
Enter a whole number (1–3999) or type Roman numeral characters. The field only accepts valid input and converts as you type.
See the breakdown
Every Roman symbol is shown individually with its numeric value so you can see exactly how the total is composed.
Copy and use
Click the copy button to grab the result. Use the quick-example buttons to explore common values instantly.
Why use this converter?
- Your input never leaves your device — all conversions run entirely in your browser; nothing you type is ever stored or transmitted to a server.
- Instant results as you type — no button to press, no round-trip to a server.
- Strict validation — the converter uses round-trip checking to accept only canonical, well-formed Roman numerals, so you always get correct output.
- Symbol breakdown — see how each Roman character contributes to the total, making it a useful learning tool.
How to use the Roman Numeral Converter
- Select a conversion direction with the tabs at the top.
- Arabic → Roman: type any whole number from 1 to 3 999. The Roman numeral appears instantly.
- Roman → Arabic: type Roman numeral characters (M, D, C, L, X, V, I). Only standard subtractive-notation numerals are accepted.
- Read the result and breakdown — each symbol is shown with its individual value.
- Click Copy to copy the result to your clipboard.
Roman numeral reference table
The seven symbols and the six standard subtractive pairs used in classical Roman notation:
| Symbol | Value | Notes |
|---|---|---|
| I | 1 | Subtracted before V and X (IV = 4, IX = 9) |
| V | 5 | Never subtracted |
| X | 10 | Subtracted before L and C (XL = 40, XC = 90) |
| L | 50 | Never subtracted |
| C | 100 | Subtracted before D and M (CD = 400, CM = 900) |
| D | 500 | Never subtracted |
| M | 1000 | Maximum of three consecutive (MMM = 3000) |
Common year conversions
Roman numerals appear frequently in film credits, clock faces, and formal documents. Here are common years:
| Year | Roman numeral |
|---|---|
| 1999 | MCMXCIX |
| 2000 | MM |
| 2010 | MMX |
| 2020 | MMXX |
| 2024 | MMXXIV |
| 2025 | MMXXV |
| 2026 | MMXXVI |
| 3999 | MMMCMXCIX |
Understanding subtractive notation
Standard Roman numerals use subtractive notation for six special cases to avoid four-in-a-row repetition:
- IV (4) — I before V subtracts 1 from 5.
- IX (9) — I before X subtracts 1 from 10.
- XL (40) — X before L subtracts 10 from 50.
- XC (90) — X before C subtracts 10 from 100.
- CD (400) — C before D subtracts 100 from 500.
- CM (900) — C before M subtracts 100 from 1000.
Only these six pairs are canonical. Forms like IIII (4), VV (10), or MMMM (4000) are non-standard and rejected by this converter.
Frequently Asked Questions
What is the Roman numeral for 2026?
2026 in Roman numerals is MMXXVI. Breakdown: MM = 2000, XX = 20, VI = 6.
What is the highest number in Roman numerals?
Using standard notation (no overbar/vinculum), the highest is 3999 = MMMCMXCIX. This converter supports the full 1–3999 range.
How does subtractive notation work?
When a smaller numeral appears directly before a larger one, you subtract it. The six standard subtractive pairs are: IV (4), IX (9), XL (40), XC (90), CD (400), CM (900). All other characters are additive.
Why is my Roman numeral rejected?
The converter uses round-trip validation: it parses your input, re-encodes it, and checks the strings match. Non-standard forms like IIII (should be IV) or VX (non-standard) will fail. This ensures only canonical numerals are accepted.
Is my input stored or sent to a server?
No. Every conversion runs entirely inside your browser using JavaScript. Nothing you enter is ever sent to or stored on a server.
Can I convert numbers larger than 3999?
Standard Roman numerals without an overbar only go up to 3999. Numbers from 4000 onward require a vinculum (overbar) or alternative notation not covered by the classical system. This tool sticks to the 1–3999 standard range.
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