Roman Numeral Converter

Convert numbers to Roman numerals and back, with strict validation.

Convert numbers to Roman numerals and back, with strict validation. Free and 100% private — runs entirely in your browser, nothing is ever uploaded.

About Roman Numeral Converter

The Roman Numeral Converter is a free, two-way tool that turns ordinary numbers into Roman numerals and decodes Roman numerals back into numbers, covering the standard range of 1 to 3999. It uses strict canonical validation, so it accepts IV but rejects non-standard forms like IIII, and it includes a symbol-value reference (I, V, X, L, C, D, M) right on the page. Everything runs entirely in your browser, so nothing you type is ever uploaded.

How to use Roman Numeral Converter

  1. To convert a number, type a whole number from 1 to 3999 into the Number to Roman field (for example, 2024) and read the Roman numeral result instantly.
  2. To decode a Roman numeral, type it into the Roman to Number field (for example, MMXXIV); it is auto-capitalized, and the decimal value appears below.
  3. Click any Copy button next to a result to put the converted value on your clipboard.
  4. Use the example chips (4 to IV, 49 to XLIX, 2024 to MMXXIV, 3999 to MMMCMXCIX) to auto-fill and see how the conversion works.
  5. Check the Symbol values table to learn each letter's worth and how a smaller symbol before a larger one subtracts (IV = 4, IX = 9).
  6. If you see an error, fix the input: numbers must be whole and within 1 to 3999, and Roman numerals must be in canonical form (IV, not IIII).

Frequently asked questions

What range of numbers does it support?
It handles whole numbers from 1 to 3999, which is the standard range for classical Roman numerals. Roman numerals have no zero and cannot represent 0, negatives, or fractions, and they cap at MMMCMXCIX (3999).
Why does it reject IIII when clocks sometimes use it?
The converter validates strict canonical form, where 4 must be written as IV, not IIII. Clock faces use IIII as a stylistic exception, but the standard rule subtracts a smaller symbol placed before a larger one, so the tool only accepts the canonical spelling.
What do the Roman numeral letters mean?
The seven symbols are I (1), V (5), X (10), L (50), C (100), D (500), and M (1000). When a smaller symbol comes before a larger one it subtracts, so IV is 4, IX is 9, and XL is 40. The on-page Symbol values table shows all of these.
Is my input sent to a server?
No. The Roman Numeral Converter runs 100% in your browser. The conversion math happens locally on your device, nothing is uploaded, and you can even use it offline once the page has loaded.
How do I write a year like 2024 in Roman numerals?
Type 2024 into the Number to Roman field and you get MMXXIV (MM = 2000, XX = 20, IV = 4). You can also click the 2024 example chip to fill it instantly, then copy the result.