Roman Numeral Converter

Convert numbers to Roman numerals and back, following the subtractive rules so 4 comes out as IV and 1994 as MCMXCIV rather than as a row of ones.

How to use
  1. Type an Arabic number or a Roman numeral.
  2. The conversion appears immediately.
  3. Copy the result.
Frequently asked questions
Why is 4 written IV rather than IIII?
Subtractive notation: a smaller symbol before a larger one is subtracted. IIII does appear on clock faces, but IV is the standard form everywhere else.
What is the largest number it handles?
3999, which is MMMCMXCIX. Standard Roman numerals have no symbol above M, so larger values need the overline notation that is rarely used today.
Is there a zero?
No. Roman numerals have no symbol for zero and no way to write one, which is a large part of why positional arithmetic took over.
Which subtractions are allowed?
Only IV, IX, XL, XC, CD and CM. You cannot write IL for 49; it is XLIX, because the subtracted symbol must be one or two steps below.
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