Roman Numeral Converter — Number to Roman Numeral Online

Roman Numeral Converter — Number to Roman Numeral Online. Free online Roman numeral converter. Instantly convert numbers to Roman numerals and Roman numerals to numbers. Supports 1–3999. No upload, 100% private.

Our free Roman numeral converter handles bi-directional conversion between Arabic numbers and Roman numerals in your browser — no upload, no account, instant results.

How Roman Numerals Work I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1000 Subtractive notation: IV = 4, IX = 9, XL = 40, XC = 90, CD = 400, CM = 900 Standard Roman numerals cover 1 to 3999 (MMMCMXCIX) Common Use Cases Chapter and section numbering in books and documents Copyright years on film titles and TV shows Clock and watch face numerals Super Bowl and Olympic Games numbering Monarchs and popes (Henry VIII, Pope John XXIII) Arabic to Roman Numeral Examples 1 = I, 4 = IV, 9 = IX, 14 = XIV, 40 = XL, 90 = XC 2024 = MMXXIV, 1999 = MCMXCIX, 3999 = MMMCMXCIX

Frequently asked questions

How do I convert a number to Roman numerals?

Type a whole number from 1 to 3999 in the Arabic to Roman field. The Roman numeral appears next to it, for example 2024 becomes MMXXIV, and Copy puts it on your clipboard.

How do I convert Roman numerals to numbers?

Type the numeral in capital letters in the Roman to Arabic field, such as XLII, and the number 42 appears beside it. Click Copy to copy the result.

Why is my Roman numeral marked invalid?

The converter only accepts standard subtractive notation in uppercase letters. Lowercase input such as xlii, non-standard forms such as IIII or IC, and anything above MMMCMXCIX (3999) are rejected as Invalid Roman numeral.

Why is the maximum 3999?

Standard Roman numerals have no symbol above M (1000) and allow at most three M in a row, so MMMCMXCIX, which is 3999, is the largest regular value. Larger numbers historically used overlines, which are not supported here, and there is no Roman numeral for zero.

How do Roman numeral subtraction rules work?

A smaller symbol placed before a larger one is subtracted: IV is 4, IX is 9, XL is 40, XC is 90, CD is 400 and CM is 900. Only I, X and C are used this way, and only before the next two larger symbols.

How to use this online tool

Roman Numeral Converter — Number to Roman Numeral Online is designed for fast browser workflows when you need to format, validate, convert, decode, encode, generate, or inspect data without opening a heavy desktop app. Start with the input field or visible options, review the result, then copy or download the output for the next step.

Private processing in your browser

Roman Numeral Converter — Number to Roman Numeral Online keeps the normal processing step local in your browser. That is useful for code snippets, tokens, documents, configuration values, text samples, and other material that should not be sent to a remote service unless you explicitly choose to share it.

When this tool is useful

Use Roman Numeral Converter — Number to Roman Numeral Online for repeatable developer tasks, technical documentation, QA checks, quick conversions, debugging, content cleanup, and internal team workflows. The page focuses on clear inputs, immediate feedback, and output that is easy to reuse in code, reports, tickets, emails, or notes.

Practical tips

Before copying the final result, check important details such as spacing, casing, filenames, encoding, token structure, line breaks, or output format. Small checks prevent mistakes when the result is reused in source code, API requests, documentation, spreadsheets, or shared files.