- Number to Roman — Enter any number from 1 to 3,999 in the left panel. The Roman numeral equivalent appears instantly.
- Roman to Number — Enter a Roman numeral (e.g., MMXXIV) in the right panel. The Arabic number appears instantly. Invalid numerals are flagged.
- Reference Chart — The chart at the top shows the 7 basic Roman numeral symbols and their values for quick reference.
- Copy — Click 'Copy' to copy either result to your clipboard.
Roman Numeral Converter — Convert Between Roman and Arabic Numbers
The Roman Numeral Converter is a free, instant-use tool for converting between Roman numerals and Arabic (decimal) numbers. Whether you're studying history, working on academic papers, decoding dates on buildings and monuments, or just curious about how Roman numerals work, this tool provides instant bidirectional conversion with validation.
The converter supports numbers from 1 to 3,999 and validates all Roman numeral input to ensure correct notation. All calculations run in your browser — no data is sent to any server.
How Roman Numerals Work
The Roman numeral system uses seven basic symbols to represent numbers. Unlike our decimal system which uses positional notation, Roman numerals are additive and subtractive:
- I = 1
- V = 5
- X = 10
- L = 50
- C = 100
- D = 500
- M = 1,000
Rules for Roman Numerals
- Additive Rule — Symbols are generally written largest to smallest, left to right, and their values are added: XVII = 10 + 5 + 1 + 1 = 17.
- Subtractive Rule — When a smaller value precedes a larger value, it is subtracted. Only I, X, and C can be subtracted: IV = 4, IX = 9, XL = 40, XC = 90, CD = 400, CM = 900.
- Repetition Limit — I, X, C, and M can be repeated up to 3 times. V, L, and D are never repeated. IIII is invalid (use IV), XXXX is invalid (use XL).
- No Zero — Roman numerals have no symbol for zero. The system starts at 1.
- Maximum — Standard notation goes up to 3,999 (MMMCMXCIX). Numbers above this require a vinculum (overline) notation.
Common Roman Numerals
- 2024 = MMXXIV
- 2000 = MM
- 1999 = MCMXCIX
- 1776 = MDCCLXXVI
- 500 = D
- 100 = C
- 50 = L
- 14 = XIV
- 9 = IX
- 4 = IV
Features
- Bidirectional — Convert numbers to Roman or Roman to numbers in separate panels.
- Real-Time — Results appear as you type with no delays.
- Validation — Invalid Roman numerals (like IIII or VV) are detected and flagged.
- Reference Chart — Quick visual reference of the 7 basic symbols.
- Copy — Copy results to clipboard with one click.
Common Use Cases
- Education — Help students learn and practice Roman numeral conversion.
- History — Decode dates on buildings, monuments, and historical documents.
- Academic Writing — Generate Roman numerals for outlines, page numbers, and chapter headings.
- Design — Create Roman numeral text for clocks, tattoos, and decorative elements.
- Film & Media — Decode copyright years in movie credits (e.g., MCMXCIX = 1999).
Privacy
All conversions run in your browser. No data is transmitted. Works offline.