Roman Numeral Converter

Convert numbers to Roman numerals and Roman numerals back to numbers, for years, names, clocks and outlines.

100% client-side · nothing is uploaded

Loading tool…

Quick answer

Roman Numerals is a free, private online tool that lets you convert between Arabic numbers and Roman numerals (1-3999). It runs entirely in your browser, so nothing you enter is uploaded to a server.

How to use the Roman Numerals

Enter the number you want to convert in the Value field.
Pick the unit you're converting From and the unit you want To.
Read the converted result, or use ⇅ to swap the two units.
Check the All units table to see your value expressed in every supported unit at once.

Privacy: this tool runs entirely in your browser. Your input is never sent to, received by, or stored on any server — there are no uploads and no tracking of what you enter.

About Roman Numerals

How Roman numerals work

Roman numerals combine letters: I=1, V=5, X=10, L=50, C=100, D=500, M=1000. Smaller before larger means subtract (IV=4, IX=9).

The range

Standard Roman numerals cover 1 to 3999. There is no zero and no standard way to write very large numbers without extensions.

Where you see them

Clock faces, book chapters, movie copyright years, monarch names (Henry VIII) and the Super Bowl.

Frequently asked questions

What is the largest Roman numeral?

In standard form, 3999 (MMMCMXCIX).

Is there a Roman zero?

No — the Romans had no symbol for zero.

How is 2024 written?

MMXXIV.

Understanding Roman Numerals in depth

What Roman numerals are

Roman numerals are the number system of ancient Rome, still used today for decoration, dates and naming. They combine seven letters — I=1, V=5, X=10, L=50, C=100, D=500, M=1000 — to build other numbers. This converter translates between ordinary (Arabic) numbers and Roman numerals in both directions.

How the system works

Numerals are generally written largest to smallest and added together, so XVII is 10+5+1+1 = 17. The clever twist is subtractive notation: when a smaller numeral precedes a larger one it is subtracted, so IV is 4 (5−1) and IX is 9 (10−1). This avoids long runs like IIII. The same rule gives XL=40, XC=90, CD=400 and CM=900.

The range and the missing zero

Standard Roman numerals cover 1 to 3999 (MMMCMXCIX). There is no symbol for zero — the concept did not exist in Roman mathematics — and no standard way to write very large numbers without special overline notation. This converter works within the conventional 1–3999 range, which covers virtually all everyday uses.

Where you still see them

Roman numerals appear on clock faces, in book chapter and page numbering, in film and TV copyright years, on building cornerstones, in the names of monarchs and popes (Henry VIII, Elizabeth II), and famously in Super Bowl numbering. Reading them is a genuinely useful everyday skill.

Everyday uses

Convert a year to Roman numerals for a design or tattoo, decode the date on a monument or film credit, number an outline or appendix, or help with schoolwork. For example, 2024 is MMXXIV. Everything runs locally in your browser.