Roman numeral converter
Read a chapter number, check a year on an inscription, or create a heading. Convert standard Roman numerals with an explicit supported range.
Roman numeral converter
Runs on your deviceThe supported notation
The tool uses I, V, X, L, C, D, and M with conventional subtractive pairs such as IV, IX, XL, XC, CD, and CM. Four is IV, nine is IX, and 2026 is MMXXVI. Values must be from 1 to 3999. The calculator does not use an overline notation for larger values or provide a Roman symbol for zero.
Decoding also checks the spelling
The decoder accepts lowercase input by converting it to uppercase first. It then checks whether the decoded value converts back to the same standard form. This rejects a string such as IIX instead of guessing that the author meant eight. Historical inscriptions and clock faces sometimes use other conventions, so a rejected form may still have appeared in a particular context.
Use the form expected by your document
Roman numerals can be a numbering style rather than the actual stored value. A word processor may handle them automatically for front matter or headings. If your source is a historical artifact, do not silently modernize its inscription just because a converter prefers another form. This tool provides a predictable standard representation, not a complete account of every historical numbering practice.
Worked examples
| Number | Roman numeral | Note |
|---|---|---|
| 49 | XLIX | 40 plus 9 |
| 2026 | MMXXVI | 2000 plus 20 plus 6 |
Good questions.
Why is IIII rejected?
The tool uses standard subtractive IV for four. Some clocks and historical sources use other conventions.
Can it convert zero or negative numbers?
No. Its supported range is the positive integers 1 through 3999.
Can I type lowercase numerals?
Yes. The decoder normalizes them to uppercase.
Updated 5 November 2026 · Methods & corrections