Roman Numeral Converter
Convert any number (1–3,999,999) to Roman numerals or back — with the standard notation rules.
100% free
No sign-up
Private · runs in your browser
How to use the free online roman numeral converter
- Type a number to convert to Roman numerals.
- Or paste Roman numerals to get the number.
- Result converts live in both directions.
- Copy instantly.
About this tool
Convert Arabic numbers (1, 2, 3…) to Roman numerals (I, II, III…) and back. Supports values up to 3,999,999 with proper subtraction rules (IV, IX, XL, XC, CD, CM) and decade notation for large numbers. Perfect for clocks, movies, book chapters, sports events and history class.
Key features
- Both directions
- Standard rules (IV, IX, XL…)
- Up to 3,999,999
- Instant conversion
Privacy first: every calculation and generation runs 100% locally in your web browser using the Web Crypto API. Your input never touches a server — nothing is stored, logged or sold.
Frequently asked questions
Symbols combine additively: I=1, V=5, X=10, L=50, C=100, D=500, M=1000. A smaller value before a larger one subtracts (IV=4, XC=90).
XL = 50 − 10 = 40. Using subtractive notation (IV, IX, XL, XC, CD, CM) keeps numerals short — four same symbols in a row are not allowed.
Up to 3,999,999 using standard notation with a vinculum (overline) for thousands. Beyond that, notation conventions differ.
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