Roman Numeral Converter
Convert numbers to Roman numerals and back, from 1 to 3,999,999.
Convert Numbers to Roman Numerals and Back
Roman numerals survive in film copyright dates, book chapters, monarch names, clock faces and Super Bowl branding. Reading them depends on one rule people routinely forget: a smaller symbol placed before a larger one is subtracted, so IV is four and VI is six.
This converter works in both directions and validates strictly. A malformed numeral like IIII or VX is rejected rather than guessed at, because the check confirms the value converts back to exactly the string you typed.
Key features
- Both directions at once — number to numeral and numeral to number, in separate panels.
- Strict validation — a round-trip check rejects malformed numerals instead of silently accepting them.
- Extended range — up to 3,999,999 using the vinculum (overline) convention for thousands.
- Symbol reference — the seven Roman symbols and their values, always on screen.
This tool runs entirely inside your browser using native Web APIs. Your files and text are never uploaded to a server, never logged and never shared with third parties.
How to use: Roman Numeral Converter
- Enter a number to convert to Roman
Any whole number from 1 to 3,999,999. The numeral appears immediately. - Or type a Roman numeral
Use the second panel. Case does not matter — it is normalised for you. - Watch for validation warnings
If a numeral is malformed the tool says so and explains the rule that was broken. - Copy the result
Each output has its own copy button.
Technical specifications
| Processing location | Entirely in your browser — no server round trip |
|---|---|
| Data uploaded | None. Files and text never leave your device |
| Price | Free — no account, no trial, no usage cap |
| Category | Converters |
| Works offline | Yes, once the page has loaded |
| Browser support | Chrome 90+, Edge 90+, Firefox 90+, Safari 15+ |
| Interface languages | English, 中文, हिन्दी, Español, العربية |
Frequently asked questions
How do Roman numerals work?
Seven symbols: I=1, V=5, X=10, L=50, C=100, D=500, M=1000. Values are added left to right, except when a smaller symbol precedes a larger one, in which case it is subtracted — IV is 4, IX is 9, XL is 40.
Why is 4 written IV and not IIII?
Standard notation limits any symbol to three consecutive repeats and uses subtraction instead. IIII does appear on many clock faces for visual balance, but it is not the standard form and this tool rejects it.
What is the largest Roman numeral?
In standard notation, 3,999 (MMMCMXCIX), because there is no symbol for 5,000. Larger values use a vinculum — an overline meaning "multiply by 1,000" — which is how this tool reaches 3,999,999.
How do I write the current year?
2026 is MMXXVI: two thousands (MM), two tens (XX), a five (V) and a one (I). Enter any year in the number field to see it converted.