First value · other representations
Numbers & representations
How it works
Roman numerals combine I, V, X, L, C, D and M. Subtractive pairs such as IV, IX and XL express 4, 9 and 40. This tool uses standard modern notation.
What you can do
Select the direction and the numeric base. Convert a list in either direction. Lowercase Roman input is accepted and generated numerals use uppercase.
How to use it
- Choose numbers to Roman or Roman to numbers, then set the numeric base. For 2026 ↔ MMXXVI, use base 10.
- Paste one value per line or open a UTF-8 text file.
- Select Convert, inspect the result, then copy or download TXT. Changes clear old results. Undo restores your previous input and settings.
Errors and limits
The supported range is 1–3999. Zero, negatives, overbars and historical variants are not supported. IIII and IIV are rejected; accepted forms must match canonical subtractive notation.
Limits: 200,000 input characters, 500 values and 1,000,000 output characters. The entire batch stops on an invalid line.
Each numeric input accepts at most 1,000 digits. Intermediate integer arithmetic is bounded to 16,384 bits.
Frequently asked questions
Why does the converter reject IIII?
IIII appears on some clock faces, but the standard subtractive form of 4 is IV. This validator intentionally follows that convention so the result has one unambiguous spelling.
Are my values uploaded?
No. Processing and file reading happen in this browser tab. Values are not placed into URLs or sent to a conversion service. Downloaded files remain under your control.