Roman Numeral Converter
Numbers to Roman numerals, and back again.
Runs entirely in your browser — nothing you enter is uploaded or sent to a server.
Standard notation covers 1 to 3,999. Historical inscriptions used variants this tool treats as invalid — real Roman usage was less consistent than the modern rules suggest, so for anything historical check the source rather than assuming the tool is right. Read our full disclaimer.
About this tool
Converts in both directions, from 1 to 3,999. Going out, it uses proper subtractive notation — 4 is IV, not IIII, and 1994 is MCMXCIV — so the result is the canonical form rather than a string of repeated letters. Coming back, it validates: a simple left-to-right parser will happily read IIII, VV or IC and hand you a number, which is how bad converters appear to work on input that no Roman ever wrote. This one re-encodes what it parsed and checks the two match, so anything non-standard is rejected with a reason instead of quietly accepted. The seven symbols and a few landmark values are on the page, so it doubles as a reference when you're reading a clock face, a film copyright date or a chapter heading.
Example
1994 is MCMXCIV: M is 1000, CM is 900, XC is 90 and IV is 4. Each of those pairs is a subtraction — the smaller symbol before the larger one means 'take it away'.
How to use
- 1Choose the direction: number to Roman, or Roman to number.
- 2Type the value — Roman input is case-insensitive.
- 3Copy the result, or tap one of the examples to see how a tricky one is built.
Features
- Both directions, with case-insensitive input.
- Proper subtractive notation — IV, IX, XL, XC, CD, CM.
- Rejects malformed numerals like IIII and IC rather than guessing.
- A symbol reference and landmark examples on the page.
Frequently asked questions
Why is 4 written IV and not IIII?
Subtractive notation: a smaller symbol placed before a larger one is subtracted from it, so IV is 5 − 1. It's the standard form and the one this tool produces. IIII does appear in the wild — famously on many clock faces, where it balances the VIII opposite — but it isn't the canonical written form.
Why won't it accept IC for 99?
Because subtraction is only allowed from the next one or two symbols up: I can precede V and X, X can precede L and C, and C can precede D and M. I before C isn't permitted, so 99 is XCIX — ninety (XC) plus nine (IX).
Why does it stop at 3,999?
Because 4,000 needs a vinculum — a bar over a numeral meaning 'multiply by a thousand' — and there is no agreed way to write that in plain text. Tools that claim to go higher usually just emit MMMM and beyond, which isn't standard notation. We'd rather refuse than invent a convention.
Is there a Roman numeral for zero?
No. The system has no symbol for zero and no concept of it as a number — it was built for counting and recording quantities, not for arithmetic. Medieval scribes occasionally wrote N, for nulla, but it was never part of the numeral system itself.
What are the seven symbols worth?
I is 1, V is 5, X is 10, L is 50, C is 100, D is 500 and M is 1,000. Everything else is built from those by adding symbols left to right, with the six subtractive pairs as the exception.
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