Roman Numeral Converter
Convert between Roman numerals and Arabic numbers. Supports values from 1 to 3999 with input validation.
Quick Reference
About Roman Numeral Converter
Our Roman Numeral Converter is a free online tool that converts between Roman numerals and Arabic (decimal) numbers. Roman numerals use seven basic symbols — I (1), V (5), X (10), L (50), C (100), D (500), and M (1000) — combined through additive and subtractive notation to represent numbers from 1 to 3999.
The converter validates input on both sides. When converting Roman numerals, it checks for valid symbol sequences and proper subtractive combinations (like IV for 4, IX for 9, XL for 40, etc.). When converting numbers, it accepts any integer from 1 to 3999 — the practical limit of standard Roman numeral notation.
Roman numerals are still widely used today in book chapters, movie sequels, clock faces, outlines, royal names, and formal documents. Understanding how to read and convert them is a useful skill in many contexts.
Frequently Asked Questions
Q Why is the maximum number 3999?
Standard Roman numerals can only represent numbers up to 3999 (MMMCMXCIX). This is because the largest symbol is M (1000), and you cannot have more than three of the same symbol in a row. While extended notation with a bar over symbols (indicating multiplication by 1000) exists, it's not universally supported in digital text, so this tool uses the standard range of 1-3999.
Q What are the subtractive rules in Roman numerals?
Roman numerals use subtractive notation to avoid four repeated characters. The rules are: I can be placed before V (5) and X (10) to make 4 and 9; X can be placed before L (50) and C (100) to make 40 and 90; C can be placed before D (500) and M (1000) to make 400 and 900. For example, 4 is IV (not IIII), 9 is IX (not VIIII), and 90 is XC (not LXXXX).
Q Is there a Roman numeral for zero?
No, there is no Roman numeral for zero. The Roman numeral system is not a positional numeral system and doesn't have a symbol for zero. The concept of zero as a number was developed in India and came to Europe through Arabic mathematics, long after the Roman numeral system was established. In ancient Rome, the Latin word "nulla" (meaning "none") was used to indicate the absence of a quantity.