Roman Numeral Converter

How to use

1. 1Type a number (for example 2026) or a Roman numeral (for example MMXXVI) into the input. The tool detects which way to convert automatically.
2. 2Read both the Roman numeral and the decimal value side by side, with a Copy button on each so you can paste the result wherever you need it.
3. 3Use the quick buttons to load common values like the current year, a milestone number, or a sample Roman numeral.
4. 4Switch on Extended notation if you need values above 3,999. Each pair of parentheses around a chunk multiplies its value by 1,000.
5. 5Switch to Batch mode and paste a column of values to convert many lines at once. Mixed input (numbers and Roman numerals together) is supported.
6. 6Browse the reference chart for 1 to 30, milestone numbers, common years, and the seven base letters at the bottom of the page.

About this tool

Roman Numeral Converter is a bidirectional translator between Arabic numbers and Roman numerals that runs entirely in your browser. The direction is detected automatically: type a number like 2026 to see its Roman form, or type Roman letters like MMXXVI to see the value. The standard mode covers the classical range of 1 through 3,999 using subtractive notation (the canonical form: IV not IIII, IX not VIIII, XL not XXXX, XC not LXXXX, CD not CCCC, CM not DCCCC). An extended mode unlocks values up to 3,999,999,999 using parentheses notation, where each pair of parentheses around a chunk multiplies it by 1,000 (so (M) is 1,000,000 and ((M)) is 1,000,000,000), keeping the result plain-text and copy-pasteable in any document or design tool. Roman numeral input is validated with a round-trip canonical check, so common mistakes (IIII for 4, VV for 10, IL for 49) are caught with a specific error that suggests the correct form. A batch mode accepts a column of values pasted from a spreadsheet (one per line) and returns a parallel column of conversions, with mixed input supported so a list combining numbers and Roman numerals is converted correctly line by line. Quick presets cover the most common reasons people search this tool: the current year, recent years, milestone numbers, and well-known Roman forms. A built-in reference chart shows 1 through 30, the milestone tens and hundreds up to 1,000, and a curated set of years that come up most often, plus the seven base letters (I, V, X, L, C, D, M) with their values for at-a-glance recall. Useful for picking a tattoo or jewelry inscription, dating a wedding or anniversary in Roman numerals, decoding the credits or copyright year on a film or book, naming numbered chapters or volumes, working out a clockface design, helping with school maths homework, and any time you need to translate between the two systems with confidence. Conversion is performed entirely in your browser, so the dates, numbers, and lists you paste here never leave your device.

Free to use. Works in your browser. No signup, no login.