Roman Numeral Converter
Convert between Roman numerals and decimal numbers
Roman Numeral Converter
Examples
Roman Numeral Rules
Symbol Values
Roman numerals use seven basic symbols: I (1), V (5), X (10), L (50), C (100), D (500), and M (1000).
Additive Principle
Symbols are generally written from largest to smallest, left to right. Example: XVI = 10 + 5 + 1 = 16
Subtractive Principle
When a smaller symbol appears before a larger one, subtract the smaller value. Example: IV = 5 - 1 = 4
Repetition Limit
No symbol can be repeated more than three times in a row (except for M). Example: III is valid, IIII is not.
Subtractive Combinations
Only specific subtractive combinations are valid: IV (4), IX (9), XL (40), XC (90), CD (400), CM (900).
Limits
The standard system can only represent numbers from 1 to 3999. Zero and negative numbers are not representable.
Roman Numeral History
Roman numerals originated in ancient Rome and remained the predominant number system in Europe well into the Late Middle Ages. They are still used today in specific contexts such as clock faces, book chapters, movie sequel numbers, and outlines.
The system is based on seven symbols: I, V, X, L, C, D, and M, which represent 1, 5, 10, 50, 100, 500, and 1000 respectively. Numbers are formed by combining these symbols using additive and subtractive principles.
The classic Roman numeral system does not have a symbol for zero and cannot express negative numbers. In its standard form, it can only represent numbers from 1 to 3,999, though various extensions have been developed for larger numbers.
Modern Usage
- Super Bowl numbers (e.g., Super Bowl LVI = 56)
- Movie sequels (e.g., Rocky IV)
- Clock faces and watch dials
- Book chapters and outlines
- Names of monarchs and popes (e.g., Queen Elizabeth II)
- Copyright dates in movie credits
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Conversion Breakdown
About the Roman Numeral Converter
Convert between Roman numerals and decimal numbers All conversions run instantly in your browser and nothing you enter is sent to a server.
Common Conversion Formulas
| From | To | Formula |
|---|---|---|
| Basic Symbols | Roman Numerals | I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1000 |
| Addition Rule | Symbols in Descending Order | XVI = 10 + 5 + 1 = 16 |
| Subtraction Rule | Smaller Symbol Before Larger | IV = 5 - 1 = 4, IX = 10 - 1 = 9, XC = 100 - 10 = 90 |
| Repetition Limit | Maximum Repetitions | No more than 3 consecutive identical symbols (III is valid, IIII is not) |
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