A short companion for Roman Numerals: when it is useful, what it expects, and what to check before using the result.
What it does
Convert between Roman numerals and decimal numbers, using the subtractive notation for 4, 9, 40, 90, 400 and 900. It covers 1 to 3999, which is the range the plain notation reaches without an overline.
Use the tool
Open Roman Numerals, add the input the tool asks for, run it, and check the output before using it elsewhere.
Input and output
- Input: text.
- Output: text.
- Category: Convert.
Privacy and processing
Processing happens locally in your browser. This tool does not upload the input to ilham.dev.
Questions
Why does it stop at 3999?
Standard Roman notation has no zero and no way to write larger numbers without an overline or a different convention. 3999 is MMMCMXCIX, the largest value the plain form expresses.
Related guide
For broader background, see Calculators and Unit Conversion.