Roman Numeral Converter
Convert Arabic numerals to Roman numerals, or Roman numerals to Arabic. Convert multiple lines at once — all processing happens inside your browser, so your values are never sent externally.
Recent conversions
Roman numeral reference and notation rules
I=1, V=5, X=10, L=50, C=100, D=500, and M=1000. Only established subtractive forms such as IV, IX, XL, XC, CD, and CM are allowed.
How to use
- Enter the values to convert, one per line, in the input box.
- Choose the conversion direction (number → Roman or Roman → number).
- Click "Convert", then copy the value in the result box with "Copy result".
Frequently asked questions
What is the maximum I can convert?
It converts 1 to 3999 following standard Roman numeral rules. Values out of range or in the wrong format are shown as a question mark.
Can I convert several at once?
Yes. Enter one per line and each line is converted in order.
Are the values I enter sent to a server?
No. All processing happens inside your browser, and the values you enter are never sent to any external server.
Practical example and verification criteria
Roman Numeral Converter: First determine whether the conversion deletes or replaces source text, only changes order, or creates a new notation; check line endings, whitespace, case, Unicode, and language-specific rules. For hard-to-reverse operations such as replace or sort, preserve a separate source copy and test the option's scope on a small sample.
Roman Numeral Converter: For a quick check, start with 49 ↔ XLIX as a small input whose result relationship you can verify directly. Confirm that the input summary, units, and options match your intent before applying the tool to real values or a copy of the source; this reduces setup mistakes.
Roman Numeral Converter: Compare line and item counts, first and last values, duplicates, and blank lines before and after conversion; when possible, reverse the conversion to see whether the source is recovered. Initial consonants, Roman numerals, slugs, and hashtags can have different allowed characters or meanings by language and platform, so match the actual target system's rules.
Roman Numeral Converter · Work record: For real work, record the input conditions, selected options, and result together. Do not assume the same state will remain after a refresh or device change. Preserve important results separately using copy, download, a screenshot, or another method the page supports, then reopen them in the target environment.
Roman Numeral Converter · Error check: If an error or unexpected result appears, reduce the input, run again with default options, and then change one condition at a time. Recording error messages and boundary values helps distinguish format issues, unsupported cases, and browser resource limits, and prevents an empty result from being mistaken for success.
Roman Numeral Converter · Scope of use: Check the page guidance for browser processing versus server lookup, storage location, and supported scope. Use sensitive source material or secrets only when strictly necessary. High-impact work such as legal, financial, or medical decisions or changes to an operational system requires current authoritative information and a separate verification process.