Roman Numeral Converter
Arabic to Roman and back, both directions.
Roman Numeral Converter turns ordinary numbers into Roman numerals and Roman numerals back into numbers, following the standard subtractive rules. It validates the input, explains which rule a malformed numeral breaks, and supports vinculum notation above 3,999. Everything runs in your browser.
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Runs entirely on your device. No file or text you enter here is uploaded. How to verify it.
How to use Roman Numeral Converter
- Type a number, or a Roman numeral.
- Read the conversion in the other direction.
- Check the breakdown showing how the numeral is composed.
Questions about Roman Numeral Converter
Why is 4 written IV and not IIII?
The subtractive rule: a smaller symbol before a larger one is subtracted. Only I, X and C may subtract, and only from the next two larger symbols — so IV and IX are valid, IL and IC are not. Clock faces that use IIII do so by tradition, not by rule.
How are numbers above 3,999 written?
Classically with a vinculum — a bar over a numeral multiplying it by 1,000. The tool renders that with an overline and also accepts the parenthesis notation used in plain text.
Is there a Roman zero?
No. The system has no symbol for zero and no way to write negative or fractional values, which is one reason positional notation replaced it.
How do I write a full date in Roman numerals?
Convert each part on its own and join them: 21 August 2026 becomes XXI · VIII · MMXXVI. The tool converts one number at a time rather than parsing a whole date, because the separator and the day-month order are a matter of taste and vary by country.
What happens if I type something like IIII or IM?
It is still read — IIII comes back as 4 — but the tool marks it as non-standard and shows the canonical spelling next to it. That distinction matters when you are checking an inscription or a film copyright line rather than writing one yourself.
Is Roman Numeral Converter really free, with no limits?
Yes. There is no account, no daily cap, no file-size tier and no watermark, because there is no server cost to recover. The site is funded by clearly disclosed partner recommendations on the Partners page, never by metering the tools.
Are my files or text uploaded when I use Roman Numeral Converter?
No. Everything is processed by JavaScript running in your browser, on your device. You can verify it: open your browser's developer tools, switch to the Network tab, and use the tool. You will see no request carrying your data — because there is nowhere for it to go.