Roman Numeral Converter
Convert Roman numerals to Arabic numbers and back. Supports 1-3999. Free, runs 100% in your browser.
Reference
How does the Roman numeral converter work?
Roman numerals use seven letters — I (1), V (5), X (10), L (50), C (100), D (500), M (1000) — and combine them with additive and subtractive rules. This tool implements the standard subtractive notation (e.g., IV = 4, IX = 9, XL = 40) and supports the conventional range of 1 to 3999. The conversion uses a greedy algorithm: at each step, subtract the largest possible value and append its symbol(s).
Roman numeral values
- I = 1, IV = 4, V = 5, IX = 9
- X = 10, XL = 40, L = 50, XC = 90
- C = 100, CD = 400, D = 500, CM = 900
- M = 1000
Common uses
- Movie credits & sequels — Star Wars Episode IX, Super Bowl LVIII.
- Clocks & watches — read traditional Roman numeral dials.
- History & dates — decode inscriptions and copyright dates.
- Outline numbering — convert section numbers in formal documents.
Privacy
All conversion runs 100% in your browser. No data is sent to any server.