Roman → Arabic Number Calculator

This calculator can handle Roman numbers from 1/12 up through 399,999,999 and 11/12.

If you do not know how to do thousands, tens of thousands, and fractions in Roman numerals, a little practice with the Arabic → Roman calculator should work as a stop-gap, until I add an ‘About Roman Numerals’ page.

For fractions, use the letter S for one half, a hyphen () for one-twelfth, an equal sign (=) for two-twelfths, and combinations of those symbols for other values: S= for 8/12, = – for 3/12, and so on. To indicate that whole numbers are to be multiplied by a thousand, you may use either vertical or slanted slash marks (| | or / /): the first is more Roman, the second may be easier not to mix up with a capital I. For Roman hundreds of thousands you will have to use square brackets ([ ]): the program will turn these into vertical slashes and an overline. It does not matter whether the numbers you input are majuscule (CXVII) or minuscule (cxvii), and spaces will be ignored. I am still working on the format checking - a complex problem - so improperly formed Roman numerals will often give incorrect results, when they should get an error message.

Translate Roman Number to Arabic:    Fraction: