How it works
A walkthrough, end to end.
- 1
Enter a number (1–3999) or a Roman numeral string.
- 2
The opposite form is shown instantly.
- 3
Standard subtractive notation (IV = 4, IX = 9) is used.
Reference
Roman numerals
I=1, V=5, X=10, L=50, C=100, D=500, M=1000. Subtractive pairs: IV, IX, XL, XC, CD, CM. Up to 3,999.
Use cases
What you can do with this.
Movie copyright dates
Decode 'MMXVI' = 2016 from end credits.
Outline numbering
Use I, II, III for sections.
Watch faces
Read clocks marked with Roman numerals.
History homework
Convert dates on monuments and texts.
Sports
Super Bowl LVIII = 58.
Royal names
Henry VIII, Louis XIV, Elizabeth II.
Book chapters
Front matter often uses Roman numerals.
Roman 2026 — what's current
Living tradition for chapters, monuments, and movies.
FAQ
Frequently asked.
3,999 (MMMCMXCIX). Standard Roman numerals don't support larger numbers.
Romans had no zero — minimum is 1 (I).
Output is uppercase. Lowercase input is accepted on parsing.
No. Conversion runs in your browser.