Free Roman Numeral Converter

1. Choose your direction. Select "Number → Roman" to convert a decimal number to Roman numerals, "Roman → Number" to convert Roman numerals to a decimal, or "Date Mode" to convert a year.

2. Enter your value. Type a number between 1 and 3,999 or a valid Roman numeral string. The conversion happens instantly as you type.

3. Copy the result. Click the Copy button to copy the converted value to your clipboard. Use the reference table to explore common values and learn Roman numeral patterns.

Roman numerals originated in ancient Rome and were the dominant number system across Europe for nearly two thousand years. Unlike our modern positional decimal system where the position of a digit determines its value, Roman numerals use a combination of letters to represent values. The system is additive and subtractive: you add values when a smaller symbol follows a larger one (VI = 5 + 1 = 6), and subtract when a smaller symbol precedes a larger one (IV = 5 - 1 = 4).

The seven symbols. Roman numerals use only seven symbols: I (1), V (5), X (10), L (50), C (100), D (500), and M (1,000). Every number from 1 to 3,999 can be expressed using combinations of these characters. The system has no symbol for zero, which is one reason it was eventually replaced by the Hindu-Arabic numeral system we use today. The concept of zero was revolutionary for mathematics and was one of the key advantages of the positional system.

Modern usage. Despite being replaced for arithmetic, Roman numerals remain widely used today. They appear on clock faces, in movie and book sequels (Star Wars Episode IV, Chapter IX), for Super Bowl numbering (Super Bowl LVIII), on building cornerstones and monuments to indicate construction years, in outlines and legal documents for hierarchical numbering, and in academic contexts for preliminary pages. The British monarchy uses Roman numerals in regnal names (Elizabeth II, Charles III).

Subtractive notation rules. Not every smaller-before-larger combination is valid. Only I can be subtracted from V and X; only X can be subtracted from L and C; and only C can be subtracted from D and M. This means you write 99 as XCIX (not IC), and 999 as CMXCIX (not IM). The converter validates these rules automatically, so you can trust that the output follows standard Roman numeral conventions.

Limitations. Traditional Roman numerals cannot represent zero, negative numbers, fractions, or very large numbers above 3,999 without extending the system with vinculum notation (a bar over a symbol to multiply by 1,000). For practical purposes, the range of 1 to 3,999 covers the vast majority of real-world uses, including all historical dates in the Common Era.