Roman Numeral Converter
Convert between numbers and Roman numerals.
What is Roman Numerals?
A bidirectional Roman numeral converter following the standard subtractive notation (IV, IX, XL, XC, CD, CM).
How it works
To Roman: greedily subtract the largest fitting numeral value. From Roman: walk left-to-right, adding values and subtracting when a smaller numeral precedes a larger one.
- Enter your input. Type or paste your input into the field above — the tool responds instantly.
- Review the result. Output updates live as you type. Everything runs entirely in your browser.
- Copy or download. Use the Copy button to grab the result, or Download to save it as a file.
Examples
Years and chapter numbers
Convert 2026 to MMXXVI — or read movie credits and outlines back into numbers with the reverse direction.
Common mistakes
Invalid subtractive forms
IIII, VV, and IC are not valid Roman numerals. The converter validates input and explains the subtractive rule (IV, IX, XL, XC, CD, CM).
Frequently asked questions
What is the subtractive rule?
A smaller numeral before a larger one subtracts: IV is 4, IX is 9, XL is 40. Only powers of ten may subtract (I, X, C).
Is there a maximum value?
Standard notation supports values up to 3,999 (MMMCMXCIX); larger numbers use overline notation, which the converter explains.