Updated: July 2026
Roman Number Converter is a free online tool that transforms decimal numbers into Roman numerals and vice versa, also showing how the result was assembled.
What is it
Roman numerals still appear in book chapters, centuries, names of events, clocks and schoolwork, but few people remember all the rules of how to form each number by heart. This tool does this translation in both directions: you type a common number (Arabic) and receive the corresponding Roman numeral, or you type a Roman numeral and receive the equivalent decimal number.
The conversion works for numbers from 1 to 3999, which is the standard range of classical Roman numerals (there is no Roman symbol for zero or negative numbers). If you enter a value outside this range or a letter combination that doesn't follow Roman rules, the tool explains the reason for the error rather than simply crashing.
How to use
- Type a number in the "Number (Arabic)" field to see the corresponding Roman numeral appear instantly.
- Or enter a Roman numeral (such as MMXXVI) in the field below to see the equivalent decimal number.
- Use the shortcut buttons "Current Year" and "Current Century" to quickly convert these two common values, without having to type.
- Copy the result with the copy button when you want to use the Roman numeral elsewhere.
How the number is broken down
Whenever the conversion is valid, the tool shows a table with the mathematical decomposition of the Roman numeral, displaying each symbol used and the value it represents, in the order in which they were added until forming the final number. For example, 1994 breaks down into M (1000) + CM (900) + XC (90) + IV (4), which helps to understand why the smaller letter appears before the larger one in some passages (the subtraction rule). If you type an invalid combination, such as repeating the letter I more than three times in a row or repeating V, L, or D, the tool points out exactly which rule was broken. Everything runs in the browser, without registration and free of charge.