Roman Numeral Converter

How it works

Each line is converted on its own, and the tool sees which way to go: a number becomes a Roman numeral, and a Roman numeral becomes a number. Roman numerals add up from left to right, except that a smaller numeral before a larger one is subtracted.

So 1984 is M (1,000) + CM (900) + LXXX (80) + IV (4): MCMLXXXIV.

Dates

Type a date with slashes, dots, dashes or bullets between the parts, and each part is converted: 12/25/2020 becomes XII/XXV/MMXX, and 5 • 12 • 2019 becomes V • XII • MMXIX. The order stays as you typed it, so write month first or day first, whichever you need. Leading zeros don’t matter: 07 is VII. A Roman date like XII.XXV.MMXX turns back into 12.25.2020.

Numbers above 3,999

Without extra marks, the largest Roman numeral is MMMCMXCIX, 3,999. Above that, a bar over the letters multiplies them by 1,000: V̅ is 5,000, X̅ is 10,000 and M̅ is 1,000,000, so 10,500 is X̅D. The tool writes and reads bars up to 3,999,999. Some fonts draw the bar slightly off, and a few apps drop it when you paste.

Checking a Roman numeral

Paste any Roman numeral and the tool reads it, in capitals, lowercase, or as Unicode’s own numeral characters like Ⅻ. Forms that aren’t standard are read with the usual rules and the tool shows the standard form: IIII, as on many clock faces, is 4, and the standard way to write it is IV.

There’s no Roman numeral for zero, for negative numbers or for fractions, so those are explained instead of converted. Nothing you type is sent anywhere.