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Roman Numeral Converter

Convert numbers to Roman numerals and back (2026 → MMXXVI); invalid numerals are flagged instantly.

Runs in your browser Free

Number → Roman numeral

MMXXVI

Numbers above 3,999 use the vinculum (overline) notation: V̅ = 5,000.

Roman numeral → number

14

Examples:

How Roman numerals work

Roman numerals use the letters I (1), V (5), X (10), L (50), C (100), D (500) and M (1000). Values are added from largest to smallest, and a smaller symbol before a larger one is subtracted: IV = 4, IX = 9, XL = 40, CM = 900. The year 2026 is written MMXXVI.

What the converter does

  • Converts numbers to Roman numerals and Roman numerals to numbers
  • Writes 1–3,999 in standard notation
  • Expresses values up to 3,999,999 with the overline (vinculum) convention
  • Flags invalid forms such as IIII or VX and suggests the correct one

Where it's used

Clock faces, book chapters, names of monarchs and popes, film copyright years, tattoo designs and homework.

How to use Roman Numeral Converter

  1. Enter a number or a Roman numeral.
  2. The conversion happens instantly.
  3. If the numeral is invalid, read the warning and the suggested form.
  4. Copy the result.

Why use this tool?

Guarantees correct, standard notation without memorising the rules.

FAQ

Why are IIII or VX considered invalid?

Standard Roman numerals use the subtractive pairs IV, IX, XL, XC, CD and CM, and no symbol repeats more than three times, so 4 is IV and VX is simply V.

Is there a zero in Roman numerals?

No, the Roman system has no symbol for zero.

How are 4,000 and above written?

A line over a symbol multiplies it by 1,000; an overlined V is 5,000.

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