Roman Numeral Converter
Convert between Roman numerals and decimal numbers easily. Roman numerals use combinations of letters from the Latin alphabet to signify values.
Decimal to Roman
Roman to Decimal
Roman Numeral Reference Table
| Symbol | Value | Description |
|---|---|---|
| I | 1 | Represents a single unit |
| V | 5 | Represents five units |
| X | 10 | Represents ten units |
| L | 50 | Represents fifty units |
| C | 100 | Represents one hundred units (Latin: centum) |
| D | 500 | Represents five hundred units |
| M | 1000 | Represents one thousand units (Latin: mille) |
Subtractive Notation
| Symbol | Value | Example |
|---|---|---|
| IV | 4 | I before V subtracts 1 from 5 |
| IX | 9 | I before X subtracts 1 from 10 |
| XL | 40 | X before L subtracts 10 from 50 |
| XC | 90 | X before C subtracts 10 from 100 |
| CD | 400 | C before D subtracts 100 from 500 |
| CM | 900 | C before M subtracts 100 from 1000 |
About Roman Numerals
Roman numerals originated in ancient Rome and remained the usual way of writing numbers throughout Europe well into the Late Middle Ages. Numbers in this system are represented by combinations of letters from the Latin alphabet.
History of Roman Numerals
The Roman numeral system dates back to approximately 500 BCE. The system was developed as a way to count and conduct trade in the Roman Empire. Unlike our modern decimal system, which is based on positional notation and uses the concept of zero, Roman numerals are based on certain letters which represent fixed values.
Rules for Roman Numerals
- Repetition: A letter can be repeated up to three times to add its value (e.g., III = 3).
- Subtractive Notation: A letter placed before one of greater value subtracts its value (e.g., IV = 4).
- Additive Notation: A letter placed after one of greater or equal value adds its value (e.g., VI = 6).
- Subtraction Rules: Only I, X, and C can be used as subtractive numerals.
- Grouping: The numeral values from left to right should be in descending order, except where subtraction is used.
Modern Uses of Roman Numerals
- Clock Faces: Many analog clocks and watches use Roman numerals.
- Book Chapters and Volumes: Often used for numbering chapters, volumes, and sections in books.
- Movie Sequels: Commonly used for sequel numbers in movie titles (e.g., Star Wars: Episode IV).
- Major Sporting Events: The Super Bowl uses Roman numerals to designate each game.
- Names of Monarchs and Popes: Used to distinguish between rulers with the same name (e.g., Pope Benedict XVI).
- Outlines and Lists: Sometimes used in outline formats and formal lists.
Limitations of Roman Numerals
While Roman numerals have historical and aesthetic value, they have significant limitations compared to our modern Arabic numeral system:
- No Zero: The Roman system has no symbol for zero, limiting mathematical calculations.
- Complexity for Large Numbers: Writing large numbers becomes unwieldy and difficult to read.
- Limited Range: Traditionally, Roman numerals can only express numbers up to 3,999 using standard notation.
- Difficult Arithmetic: Basic mathematical operations are much harder to perform than with Arabic numerals.
Fun Facts
- The year 1999 in Roman numerals is MCMXCIX, using 9 characters.
- Some Roman clocks use IIII for 4 instead of IV for aesthetic balance with VIII (8).
- The longest standard Roman numeral is MMMCMXCIX (3,999).
- Ancient Romans used specialized symbols for larger numbers, including a symbol for 5,000 and 10,000.
- In music theory, chords are often labeled with Roman numerals to indicate their function in a key.