Roman Numeral Converter — 1 to 3999
Convert between decimal integers and standard Roman notation
Runs in your browser · nothing is uploaded
What it does
Enter a whole number or a Roman numeral and view both forms. The converter follows common modern subtractive notation, which writes 4 as IV and 9 as IX. It is useful for chapter headings, dates in inscriptions and numeral exercises within the supported range.
How to use
- Enter an integer from 1 to 3999 or a Roman numeral such as MCMXCIV.
- Choose Calculate to view the decimal and Roman forms.
- Copy the result. Lowercase Roman input is accepted and converted to uppercase.
Calculation rules and limits
- The accepted symbols are I, V, X, L, C, D and M.
- Subtractive pairs are IV, IX, XL, XC, CD and CM.
- Input must match the canonical form produced by the converter. Nonstandard forms such as IIII, IC and VX are rejected.
- Zero, negative numbers, fractions, overlines and values of 4000 or greater are outside the supported notation.
Example
2026 becomes MMXXVI. MCMXCIV becomes 1994. The largest supported value is 3999, written MMMCMXCIX.
Calculations run in your browser without uploading your calculation data. Changing an input clears the previous result; choose Calculate again to get the updated answer.
FAQ
Why is IIII rejected even though it appears on clocks?
Some clock faces use an additive variant. This converter consistently validates the common subtractive form IV.
Can it convert zero or very large numbers?
No. This tool deliberately uses the 1–3999 convention without zero, overlines or extended numeral systems.
Can I enter lowercase letters?
Yes. Spaces at the ends are trimmed and lowercase Roman letters are converted to uppercase before validation.
