Roman Numeral Converter

Roman numeral conversion is the process of translating a value between the decimal (Arabic) number system and the ancient Roman system of letters. Roman numerals originated in ancient Rome and remained the usual way of writing numbers throughout Europe well into the Late Middle Ages, and they are still used today on clock faces, in book chapters, for monarch names, and in film credits.

The system is built from seven base symbols: I (1), V (5), X (10), L (50), C (100), D (500), and M (1000). Symbols are normally written from left to right in descending order of value and their values are added together, so MMXXIV means 1000 + 1000 + 10 + 10 + 4 = 2024.

Subtractive notation keeps numerals short by avoiding more than three repeats of the same symbol. When a smaller symbol is placed immediately before a larger one, its value is subtracted instead of added. Only six subtractive pairs are valid: IV (4), IX (9), XL (40), XC (90), CD (400), and CM (900).

This converter works in both directions, accepts any integer from 1 to 3999, and shows the step-by-step greedy decomposition so you can see exactly how each symbol is chosen. Because the standard system has no zero and no symbol for 4000 or above, 3999 is the practical upper limit.

Key Concepts

• Seven base symbols — I, V, X, L, C, D, and M stand for 1, 5, 10, 50, 100, 500, and 1000.
• Additive rule — symbols written in descending order are added together, as in XI = 11.
• Subtractive rule — a smaller symbol before a larger one is subtracted, as in IV = 4.
• Greedy decomposition — the largest possible value is removed from the number first, step after step.
• Range 1–3999 — the tool covers the full standard range, and there is no zero symbol.
• Bidirectional — convert Arabic numbers to Roman, or Roman numerals back to Arabic.

1. Enter an Arabic number — type any whole number from 1 to 3999 into the left field.
2. Read the Roman numeral — the right field updates instantly with the converted value.
3. Follow the steps — the step-by-step panel lists each symbol removed from the running total.
4. Convert the other way — type a Roman numeral into the right field to convert it back to an Arabic number.
5. Check the result — only valid symbols and subtractive pairs are accepted, so the output is canonical.

Roman numerals still appear in many everyday and professional contexts. This converter is useful whenever you need to read or produce them accurately and quickly.

1. Reading clocks and watches — many analog clocks use Roman numerals for the hours, and this tool helps you decode them.
2. Books and outlines — chapters, volumes, and outline levels are frequently numbered with Roman numerals.
3. Copyright and release years — film and television credits traditionally show the year in Roman numerals.
4. Monarchs and popes — regnal names such as Henry VIII or Elizabeth II use Roman numerals after the name.
5. Education and homework — students learning the system can check answers and follow each decomposition step.
6. Events and tattoos — sporting events, anniversaries, and commemorative dates often use Roman numerals for a classical look.