Converting numerals...
Enter a number or Roman numeral to convert
The result will show the canonical numeral, decimal value, and symbol-by-symbol breakdown.
Roman numeral rules
How the Roman numeral converter works
This Roman numeral converter changes a whole number into standard Roman notation and converts a Roman numeral to number form. It uses canonical subtractive notation, so 4 is IV, 9 is IX, 40 is XL, 90 is XC, 400 is CD, and 900 is CM.
The calculator supports positive whole numbers up to 999,999. Traditional Roman numerals are usually taught up to 3,999; larger values here use repeated M notation because overline notation is not universally typed or displayed the same way online.
Canonical notation diagram
Subtractive notation puts a smaller symbol before a larger symbol to make values such as 4, 9, 40, and 900.
MCMXCIX breakdown
The converter groups Roman numerals into the largest valid chunks, then adds their decimal values.
Examples
| Number | Roman | Breakdown |
|---|---|---|
| 44 | XLIV | 40 + 4 |
| 944 | CMXLIV | 900 + 40 + 4 |
| 1999 | MCMXCIX | 1000 + 900 + 90 + 9 |
| 2026 | MMXXVI | 2000 + 20 + 6 |
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FAQ
What numbers can Roman numerals represent in this converter?
This tool supports positive whole numbers from 1 to 999,999. Numbers above 3,999 use repeated M notation.
Why does the converter reject IIII?
Standard canonical notation uses IV for 4. Some clocks use IIII, but this Roman numeral converter returns canonical historical math notation.
Can I convert Roman numeral to number form?
Yes. Choose Roman to number, enter a canonical Roman numeral such as MCMXCIX, and the converter returns the decimal value and breakdown.
External references