How to use this tool
Enter either a decimal integer or a Roman numeral. The converter uses standard subtractive notation: IV, IX, XL, XC, CD and CM. Nonstandard sequences such as IIII, IIV or VX are rejected instead of being silently interpreted. Lowercase input is accepted and normalized to uppercase. Zero and negative numbers have no representation in this convention.
Try these values
2026 is MMXXVI. 1994 is MCMXCIV: M is 1000, CM is 900, XC is 90 and IV is 4. XLII converts back to 42.
Read the smaller groups first
Subtractive pairs make long numerals easier to check. In MCMXCIV, read M, CM, XC and IV as 1000, 900, 90 and 4, then add them. The converter follows those standard pairs rather than allowing any smaller letter to subtract from a larger one. That is why an expression such as IC is rejected instead of being treated as ninety-nine.
Know which notation you need
Clock faces and historical inscriptions sometimes use forms that differ from modern standard notation. A clock may show IIII for four, for example. This tool deliberately uses IV and validates that same convention in reverse. It covers plain numerals up to 3999; overlines, large-number extensions and special historical forms need a different notation and should not be silently mixed with this one.
Common questions
Why is the limit 3999?
Larger numbers require conventions such as overlines, which this plain-text converter does not use.
Is IIII accepted?
No. Some clock faces use IIII, but this tool validates standard subtractive notation, where four is IV.
Can I type lowercase letters?
Yes. Valid lowercase Roman numerals are converted to uppercase.
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