A roman numeral converter maps the integers 1 through 3999 onto the standard subtractive spelling: I, V, X, L, C, D, M, plus IV, IX, XL, XC, CD, and CM. This roman numeral converter uses that range and those forms. It will not invent a bar for 4000. It will not accept IIII, VIIII, IC, or XM. Clock faces that use IIII are a design choice; they are not valid input here.
Arabic to Roman is greedy from M down to I. Roman to Arabic first checks the whole string against the standard pattern, then adds the values. Case does not matter on input. Output is uppercase. Empty input is an error. A script tag or other markup is not a numeral and is rejected.
This is not a base conversion. Bases 2–36 belong on the Number Base Converter. Roman numerals are a notation, not a radix.
Decimals such as 14.5 are rejected. Zero and 4000 are rejected. Enter converts.
2026 is MMXXVI. 14 is XIV. 44 is XLIV. 99 is XCIX. 1999 is MCMXCIX. IIII is rejected. IC is rejected. XIV as Roman to Roman is accepted and returns XIV.
2026 = MMXXVI
14 = XIV
44 = XLIV
IIII → errorIf a source used IIII, type 4 instead of asking this page to bless the clock. If you needed hex, use the Number Base Converter.
Outline headings in some books still use Roman numerals for front matter. MMXXVI is a year. Super Bowl and monarch numbers are the same mapping. This page will not add a “the 21st” ordinal word. It will not lowercase the output to match a stylesheet. Copy the uppercase result and style it elsewhere.
Unicode lookalikes and mixed Greek letters are rejected because they are not in the standard pattern. That is also how a pasted script tag fails: it is not I, V, X, L, C, D, or M in a legal order. The result row is written as text, not as HTML, so a clever numeral cannot become a page element.
4000 and 0 have no standard form on this page. Overlines for larger numbers are a different notation and are not implemented. If you need those, this is the wrong converter. Swap after a convert to check the reverse mapping: MMXXVI should return 2026, and a rejected IIII should stay rejected. Lowercase xiv is accepted and prints XIV. Spaces around a numeral are trimmed; spaces in the middle are not a valid numeral. The result row uses text, never innerHTML, so a numeral cannot become markup. Keyboard users can press Enter from the field or either list. Clear empties the field and hides the last result row.
Standard subtractive forms only (IV, IX, XL, XC, CD, CM). IIII, IC, and other informal spellings are rejected.
Whole numbers from 1 to 3999, which is I through MMMCMXCIX.
The standard form for 4 is IV. Informal clock spellings are not accepted.
99 is XCIX. Subtracting I from C is not a standard pair.
No. Use the Number Base Converter for bases 2–36.