Current year
2026
MMXXVI
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Convert whole numbers to canonical Roman numerals and back.
Quick answer
Encode whole numbers from 1 to 3,999 as canonical Roman numerals or decode them back to decimal.
Illustrative view
Canonical Roman tokens map to whole-number values in either direction.
Encode whole numbers from 1 to 3,999 as canonical Roman numerals or decode them back to decimal.
Subtractive pairs such as IV, IX, XL, XC, CD, and CM are validated by regenerating the canonical numeral.
2026
MMXXVI
MMMCMXCIX
3,999
The canonical modern form uses IV. Non-canonical repetitions are rejected to prevent ambiguous input.
Yes. The interface is responsive and works in modern mobile and desktop browsers.
No. This tool runs locally in your browser, so the values or files you provide are not sent to a ToolStack server.
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