Roman Numerals

Convert Numbers to Roman Numerals and Back, from 1 to 3999

Roman numerals still appear in movie credits, clock faces, book chapters, and Super Bowl logos. Reading them correctly means remembering the seven symbols and their subtractive rules, which trips up almost everyone past MCMXCVIII. A quick conversion saves the mental math and removes any doubt about ordering.

This tool converts any whole number from 1 to 3999 into standard Roman numerals and converts Roman numerals back into Arabic numbers. The range follows the classic convention: larger values require a bar or overline notation that this converter deliberately does not use. It validates input on both sides, so typos like IIII are flagged instead of silently accepted.

How to Convert a Number to Roman Numerals

1. Enter an Arabic number between 1 and 3999 in the input field.
2. Press convert, and the tool writes the numeral using standard subtractive notation.
3. Switch the mode to convert a Roman numeral like XLVII back to digits.
4. Check the result against the symbol table shown in the example below.
5. Copy the output for use in a document, caption, or engraving.
6. Use the validation message to correct out-of-range or malformed input.

Example Conversions

A publisher numbering the chapters of a book wants the Roman form of 1492, and a student wants to decode MMXXIV.

Reading the Symbols

The seven symbols are I (1), V (5), X (10), L (50), C (100), D (500), and M (1000). A smaller symbol before a larger one subtracts: IV is 4 and XC is 90. The same symbol is never repeated more than three times in a row, which is why 4 is IV rather than IIII. Once the pattern is clear, reading numerals becomes a matter of scanning for subtractive pairs and adding everything else, which is exactly what the converter does internally.

Tips for Correct Roman Numerals

• Know the ceiling — 3999 is the largest standard numeral; beyond it, traditional notation needs overlines.
• Use subtractive pairs — IV, IX, XL, XC, CD, and CM are the only allowed subtractions.
• Never repeat four times — IIII and XXXX are clock-face or engraving variants, not standard numerals.
• Convert in chunks — split a number into thousands, hundreds, tens, and units to build the numeral by hand.
• Decode right to left — when reading a numeral, add symbols unless a smaller one precedes a larger one.

When to Use This Tool

• Writing dates and years — style a publication year like MMXXIV for a title page or invitation.
• Numbering outlines — generate Roman numerals for section headings in reports and legal documents.
• Checking inscriptions — decode the year on a building cornerstone or a watch case.
• School assignments — verify homework answers for numeral conversion exercises.
• Game and film trivia — translate the numeral in a game title or movie sequel number.

Frequently Asked Questions