Convert Arabic numbers to Roman numerals and back with strict validation, step by step, dates, centuries, tables, batch and the overline for values above 3999.
Roman numerals use seven letters (I is 1, V is 5, X is 10, L is 50, C is 100, D is 500 and M is 1000) combined by addition and subtraction. The standard form runs from 1 to 3999 (MMMCMXCIX): only I, X and C subtract, never more than one letter, and I, X, C and M repeat at most three times. This converter reads and writes both ways, and validation is strict: IIII, VX, IC and MMMM are rejected with the broken rule and the correct form suggested, with a lenient mode for IIII, as used on clock faces. Above 3999 there is the extended notation with an overline that multiplies the letter by a thousand (I̅V̅ is 4000, up to 3,999,999), also shown in parentheses. There is also date conversion (06/10/2026 becomes VI.X.MMXXVI), century and millennium (2026 is the 21st century), chapter lists, searchable tables from 1 to 100, 1000 and 3999, line-by-line batch and an optional output in the Unicode characters Ⅰ to ⅿ.
Standard notation follows a few rules. The letters I, X, C and M can appear up to three times in a row, while V, L and D never repeat, because VV would be X. A smaller letter before a larger one is subtracted, but only six combinations count: IV, IX, XL, XC, CD and CM. Those rules explain the rejections you see: IC is not 99 because I subtracts only from V and X, and the correct form is XCIX; VX does not exist because V is never subtracted, and the value would be 5, which is written V.
When a numeral is invalid, the tool says which rule was broken, shows the literal reading of the text and suggests the standard form. Lenient mode accepts the additive forms (IIII, VIIII, XXXX, LXXXX, CCCC and DCCCC), which appear on clock faces and ancient inscriptions, and still rejects mistakes such as IC and VV.
The system has no zero. Dionysius Exiguus used the word nulla alongside Roman numerals in a manuscript of 525, and around 725 Bede, or a colleague, used the letter N, for nulla or nihil, to stand for 0 in a table of epacts written in Roman numerals. Those uses were not part of the standard notation. For fractions, the Romans used S for 1/2 (semis) and a dot for each uncia, one twelfth.
Subtraction was not always the rule either. At the Colosseum, gate 44 is marked XLIIII, with XL in subtractive form and IIII in additive form. On clock faces, 4 is often IIII and 9 is often IX, a practice that goes back to the earliest mechanical clocks, such as the Wells Cathedral clock of the late 14th century.
Paste the code into your HTML and the tool shows up on your page, without J-Kit's navigation and ads. It still runs in the browser of whoever visits your site.
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src="https://jkit.tools/embed/en-US/roman-numeral-converter"
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></iframe>These references help contextualize formulas, standards, APIs and limitations used on this page. They do not replace professional validation when a result has legal, financial, medical or operational impact.
Write the number with the largest pieces that fit, in the order M (1000), CM (900), D (500), CD (400), C (100), XC (90), L (50), XL (40), X (10), IX (9), V (5), IV (4) and I (1). For 1994: M (1000) plus CM (900) plus XC (90) plus IV (4), that is MCMXCIV. The tool shows these steps.
1000 + 900 + 90 + 4 = 1994