Roman Numeral Converter
Convert between Arabic numbers and Roman numerals. Range: 1–3999.
Roman Numeral Quiz
Type the Roman numeral for the number shown below.
What is Roman Numeral Converter?
Roman numerals are a numeral system that originated in ancient Rome and remained the dominant numeric notation in Europe until the Middle Ages, when the Hindu-Arabic numeral system (0-9) gradually replaced them. Despite being over 2,000 years old, Roman numerals are still widely used today: clock faces, chapter numbering in books, movie sequels (Rocky II, Star Wars Episode VI), Super Bowls (Super Bowl LVIII), Olympic Games (Paris MMXXIV), legal documents, formal outlines, building cornerstones, and the names of monarchs and popes (King Charles III, Pope Francis I).
The system uses seven basic symbols: I (1), V (5), X (10), L (50), C (100), D (500), and M (1000). Numbers are formed by combining these symbols using additive and subtractive notation. Subtractive notation — writing IV for 4 instead of IIII — is the standard modern form and reduces the total number of symbols needed. The largest standard Roman numeral is MMMCMXCIX (3,999); for larger numbers, a bar over a symbol multiplies it by 1,000.
Altairys's Roman Numeral Converter converts between Arabic numbers (1–3,999,999) and Roman numerals in both directions, explains the breakdown of each symbol, validates input, and shows the year any Roman numeral represents — useful for interpreting dates on buildings and monuments.
How to Use Roman Numeral Converter
- Enter a number or Roman numeral
Type an Arabic number (e.g., 2024) or a Roman numeral (e.g., MMXXIV) into the input.
- Instant conversion
The conversion happens in real time — see the result as you type.
- See the breakdown
View how each Roman numeral symbol contributes to the value.
- Copy result
Copy the converted value to clipboard with one click.
Key Benefits
Convert Arabic to Roman AND Roman to Arabic — both directions.
See exactly how each Roman numeral is decomposed into its symbolic components.
Invalid Roman numeral sequences are flagged with an error message.
Built-in reference table of all basic Roman numeral symbols and their values.
Frequently Asked Questions
I=1, V=5, X=10, L=50, C=100, D=500, M=1000. All other numbers are formed by combining these seven symbols.
Instead of writing IIII for 4, Roman numerals use IV (5 minus 1 = 4). Similarly, IX=9, XL=40, XC=90, CD=400, CM=900. A smaller symbol placed before a larger one means subtraction.
Using standard notation, the largest is MMMCMXCIX = 3,999. For larger numbers, a vinculum (bar over the symbol) multiplies by 1,000: V̄ = 5,000, M̄ = 1,000,000.
MM = 2000, XX = 20, VI = 6. Therefore MMXXVI = 2026.