Roman Numeral Converter
Convert between Arabic numbers and Roman numerals with detailed breakdowns, rules, and historical context
Conversion Mode
Choose conversion direction
Enter Arabic Number
Enter a number between 1 and 3999
Roman Numeral System
Basic symbols and values
Basic Symbols
Subtractive Forms
Key Rules
• Same symbol repeated adds values
• Maximum 3 consecutive same symbols
• Smaller before larger = subtract
• Larger before smaller = add
Roman Numeral Rules
Additive Principle
When symbols are written from largest to smallest, add their values.
XVII = X + V + I + I = 17
Subtractive Principle
Smaller symbol before larger means subtract.
IV = V - I = 4, IX = X - I = 9
Repetition Rule
Same symbol can repeat up to 3 times consecutively.
III = 3, but not IIII (use IV instead)
Subtraction Restrictions
Only I, X, and C can be subtracted. Only from the next two higher values.
I before V,X; X before L,C; C before D,M
Historical Context
Roman numerals originated in ancient Rome and were the standard numbering system in Europe until the 14th century when Arabic numerals became more widespread.
The system evolved over time. Early Romans used additive notation only, while subtractive notation (like IV for 4) became common during the Classical period.
Today, Roman numerals are still used for:
- Clock faces and watch dials
- Movie release years and sequels
- Book chapters and sections
- Formal documents and monuments
- Super Bowl games
- Monarch and Pope names
The largest number representable in standard Roman numerals is 3999 (MMMCMXCIX). Larger numbers required special notation like bars over symbols.