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Roman numeral converter

Convert numbers to Roman numerals and back, one per line. Only the strict subtractive form counts: IIII, VV and IM are rejected, and the range is 1–3999.

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Roman numeral converter is free to use as often as you like, directly from this page. It covers IIII, VV and IM are rejected, and the range is 1–3999 — adjust any of them and the result follows immediately.

How to use it

  1. Open the tool — no signup or install needed.
  2. Enter your input or adjust the available options.
  3. Get your result instantly, then copy or download it.

Frequently asked questions

What does Roman numeral converter do?

Convert numbers to Roman numerals and back, one per line. Only the strict subtractive form counts: IIII, VV and IM are rejected, and the range is 1–3999.

What does it take into account?

It factors in IIII, VV and IM are rejected, and the range is 1–3999. Change any of them and the output follows immediately.

When would I actually use this?

Getting usable data out of something that was never meant to be parsed: pulling every address out of a pasted thread, turning a column of lines into a JSON array or an SQL IN clause, renaming a hundred identifiers from snake_case to camelCase in one pass.

What is the most common mistake?

Trusting an extraction to be exhaustive. A pattern that catches every address in the sample will still miss the one wrapped across a line break, the one written with a display name, and the one an email client turned into a link — count what came out against what you expected before you use the list.

What else is filed next to it?

Roman Numeral Math Solver, ASCII code converter and Number base converter share its section. They are not variants of it — being filed together is not the same as being alike — but that is where to look if this turned out not to be the tool you wanted.

Where do the figures come from?

Extraction runs on patterns, not on a parser: it recognises the common shapes of an address, a URL or an IP rather than validating them against their specification. That is the right trade for a paste, and the wrong one for input you are about to store.

Further reading

All guides →
ExplainerRoman Numerals ExplainedSeven letters, added or subtracted. Here's what each stands for, how the subtractive pairs work, how to write any number, and where they still appear.ExplainerSemicolon, Tab, Pipe: Choosing a Delimiter That Survives the TripWhy the reader's language decides the delimiter, what the converter does to the quoting when you switch, what the sep= first line really is, and the count of quoted cells on the same export written five ways.ComparisoncamelCase, snake_case, kebab-case: Which One, and Why You Rarely Get to ChooseThe conventions are not taste. A hyphen is the minus operator, so kebab-case cannot be an identifier in most languages - which is exactly why CSS and URLs use it. Plus the acronym round-trip that silently corrupts names, and the rule that fixes it.ExplainerBig O Notation for Beginners: O(1), O(n), O(n squared), and O(log n) ExplainedBig O describes how an algorithm's work grows as input grows. Here is what O(1), O(n), O(n squared), and O(log n) mean and why the difference matters.ExplainerWhat Is UTF-8 and Unicode? Code Points, Byte Encoding, and Why UTF-8 WonUnicode assigns every character a code point; UTF-8 encodes those code points in one to four bytes. Here is how it works and why it beat the alternatives.ExplainerHow Subnet Masks Work: CIDR, Network Bits, and Usable HostsUnderstand how a subnet mask splits an IP address into network and host parts, what /24 means, and how to count usable hosts.