Roman Numeral Calculator — Convert Arabic ↔ Roman
Convert between Roman numerals and Arabic numbers instantly. Auto-detects input format. Includes full conversion rules reference.
Enter a Roman numeral (e.g. XIV) or an Arabic number (e.g. 14) — auto-detected.
Quick:
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Arabic Number
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Roman Numeral
Conversion Breakdown
Roman Numeral Reference
I1
IV4
V5
IX9
X10
XL40
L50
XC90
C100
CD400
D500
CM900
M1000
Frequently Asked Questions
What are Roman numerals?
Roman numerals are a numeral system originating in ancient Rome. They use letters from the Latin alphabet: I=1, V=5, X=10, L=50, C=100, D=500, M=1000. Numbers are formed by combining these symbols.
What is the subtractive notation rule?
When a smaller symbol appears before a larger one, it is subtracted. For example: IV = 4 (5-1), IX = 9 (10-1), XL = 40 (50-10), XC = 90 (100-10), CD = 400 (500-100), CM = 900 (1000-100). This avoids repeating symbols more than 3 times.
What is the largest Roman numeral?
The standard system represents up to 3999 as MMMCMXCIX. Beyond that, bars (vinculum) were placed above symbols to multiply by 1000, but this is rarely used today. This calculator supports 1–3999.
How do I write the year in Roman numerals?
Examples: 2024 = MMXXIV, 1999 = MCMXCIX, 2000 = MM, 1776 = MDCCLXXVI, 2025 = MMXXV.
Are Roman numerals still used today?
Yes, in specific contexts: clock faces, book chapters, movie sequel numbers (Rocky IV), year of publication in books, Super Bowl numbers, Olympic Games, and formal outlines. They are also used in chemistry (type II diabetes, etc.).