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Convert between Arabic numbers and Roman numerals, in either direction. Enter a number (1 to 3999) or a Roman numeral.

Number or Roman numeral

Converted

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To the other form.

Usage Tip

Read left to right: when a smaller symbol comes before a larger one (IV, IX), subtract it; otherwise add.

THE MATH

Built from M(1000) D(500) C(100) L(50) X(10) V(5) I(1)
Subtractive pairs: IV(4), IX(9), XL(40), XC(90), CD(400), CM(900)

Roman numerals combine letters additively, with a smaller letter before a larger one meaning subtraction.
The standard system covers 1 to 3999.

Type a number to get the numeral, or a numeral to get the number.
Numbers must be between 1 and 3999.
Non-standard numerals are still read, with the standard form noted.

Practical Notes

Roman numerals use letters for values: I is 1, V is 5, X is 10, L is 50, C is 100, D is 500, and M is 1000. Letters are normally written from largest to smallest and added together, but a smaller letter placed before a larger one is subtracted, so IV is 4 and IX is 9. The standard system covers numbers from 1 to 3999.

There is no symbol for zero, and the same letter is not repeated more than three times in a row in the standard form. You will see Roman numerals on clock faces, in book chapters and outlines, in movie copyright years, and in the names of events and monarchs. Only the standard subtractive forms are valid, so a number like 99 is written XCIX, not IC.

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