Roman Numeral Converter
Convert numbers to Roman numerals and Roman numerals back to numbers instantly, with a full reference chart and strict validation.
Roman Numeral Converter instantly converts whole numbers from 1 to 3999 into Roman numerals, and Roman numerals back into numbers, entirely in your browser. Strict validation rejects malformed numerals (like IIII or VV) and explains why. Includes a full symbol reference chart, the subtractive-notation rules, and a worked examples table. Copy or download the result. Everything runs locally. Made by FreeToolHub.
Number
Roman numeral
Roman numeral
Number
Convert between numbers and Roman numerals instantly, right in your browser.
Roman Numeral Reference Chart
Base symbols
Subtractive notation
Worked examples
Frequently Asked Questions
What are Roman numerals?
Roman numerals are a number system from ancient Rome that uses letters to represent values: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, and M = 1000. Numbers are built by combining these symbols, either by addition (VI = 6) or subtraction (IV = 4).
How do I convert a number to Roman numerals?
Switch to the Number to Roman tab, type a whole number from 1 to 3999, and the Roman numeral appears instantly. Click Convert if you typed it manually, or use Load Example to see a sample.
What is the largest number I can convert?
Standard Roman numerals go up to 3999 (MMMCMXCIX), because repeating the same symbol more than three times in a row is not valid. Larger numbers traditionally use a bar over a numeral to multiply it by 1000, which this tool does not support.
Why does my Roman numeral show an error?
The Roman to Number tab strictly validates the numeral against the real rules of Roman numeral construction. Forms like IIII (should be IV), VV (should be X), or IC (should be XCIX) are not valid Roman numerals and are rejected with an explanation.
Why can't I convert 0 or negative numbers?
The Romans had no symbol for zero, and Roman numerals only represent positive whole numbers. There is no standard Roman numeral for 0 or for any negative value.
Is my data private?
Yes. All conversion happens locally in your browser using JavaScript. Nothing you type is uploaded or sent to any server.