Roman Numeral Converter

How to use

1. Choose direction — Convert decimal to Roman or Roman to decimal
2. Enter value — Type a number or Roman numeral
3. Copy — Copy the converted result

What Is a Roman Numeral Converter?

A Roman numeral converter translates between modern Arabic numerals (1, 2, 3...) and the classical Roman system (I, V, X, L, C, D, M). Roman numerals were the standard numeric notation across the Roman Empire and persisted in European bookkeeping until the late Middle Ages. They still appear today in formal contexts like copyright dates, monarch names, and chapter numbering.

The Seven Roman Symbols

• I = 1
• V = 5
• X = 10
• L = 50
• C = 100
• D = 500
• M = 1000

Additive and Subtractive Rules

Symbols are usually added together: VI = 5 + 1 = 6, LXX = 50 + 10 + 10 = 70. When a smaller symbol precedes a larger one, it is subtracted: IV = 5 - 1 = 4, IX = 10 - 1 = 9, XL = 40, XC = 90, CD = 400, CM = 900. Only six subtractive pairs are valid in standard notation; the converter enforces these rules so the output is always canonical.

Why the Limit Is 3999

Standard Roman numerals top out at 3999 (MMMCMXCIX) because four consecutive M characters violate the rule that no symbol may repeat more than three times in a row. Larger values traditionally used a horizontal bar (vinculum) over symbols to multiply by 1000, but that notation is non-standard and rarely supported, so the converter sticks to the universally recognized range.

Where Roman Numerals Still Appear

Movie copyright years (MMXXIV = 2024), Super Bowl numbering, monarchs and popes (Elizabeth II, John Paul II), book chapters and outline levels, clock faces, building cornerstones, and formal legal citations. Reading them confidently is a small but useful skill.

Privacy

Conversion runs in JavaScript on your device. Inputs are not stored or transmitted.

Convert numbers to English words with Number to Words. Try Hex to Decimal for base-16, or Binary to Decimal for base-2.

Frequently asked questions

What range is supported?

Standard Roman numerals support 1 to 3,999 (I to MMMCMXCIX).

Is the input case-sensitive?

No. Both 'XIV' and 'xiv' are accepted.

What about zero?

Roman numerals have no symbol for zero.

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