Roman Numeral Converter

This calculator works in both directions, turning Roman numerals into ordinary numbers and ordinary numbers into Roman numerals, so you never need a conversion table by hand. You enter a single value in the box, either a Roman numeral such as MMXXIV or a whole number from 1 to 3999, and the calculator works out which type you have typed and converts it automatically. The main result shows the conversion in full, for example 2024 = MMXXIV, while two smaller results underneath give you the other form on its own and the direction of the conversion, meaning whether you went from a Roman numeral to a number or from a number to a Roman numeral. Behind the scenes the tool applies the standard rules: I, V, X, L, C, D and M stand for 1, 5, 10, 50, 100, 500 and 1000, and a smaller letter placed before a larger one is subtracted rather than added, as in IV for four or XL for forty. Because there is no Roman symbol above M, the calculator only accepts numbers from 1 to 3999, and it checks that anything you type is a properly formed numeral, flagging invalid entries such as IIII rather than guessing at an answer. It suits reading clock faces, book chapters, film credits and formal documents, or checking your own working when learning the system.

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