The Roman Numeral Converter converts whole numbers from 1 to 3,999 into standard Roman numeral notation and converts valid Roman numerals back to integers. It also shows the additions or subtractions used to build the result.
Roman numeral values
The seven basic symbols are I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, and M = 1,000. Standard subtractive pairs include IV, IX, XL, XC, CD, and CM.
When a smaller symbol appears before a larger permitted symbol, its value is subtracted. Otherwise values are added.
Number to Roman numeral example
To convert 1,994:
- Subtract 1,000 and write
M. - Subtract 900 and write
CM. - Subtract 90 and write
XC. - Subtract 4 and write
IV.
The result is MCMXCIV.
Roman numeral to number example
For XLII, the pair XL equals 50 - 10 = 40, followed by I + I = 2. The result is 42.
Valid input rules
Number-to-Roman mode accepts whole numbers from 1 through 3,999. Roman-to-number mode accepts canonical combinations that match the standard thousands, hundreds, tens, and ones pattern. Inputs such as IIII, VX, or unknown symbols are rejected.
Questions
Why is 4 written as IV instead of IIII?
Standard modern notation uses subtractive pairs for selected values: IV is one before five, so it represents 4. Some clocks use IIII, but this converter validates the conventional canonical form.
Can the converter handle zero or negative numbers?
No. The supported classical-style range is 1 to 3,999 and does not include a standard zero symbol.
Are lowercase Roman numerals accepted?
Yes. Roman input is normalized to uppercase before validation and conversion.
Limitations
The tool does not implement extended notation such as overlines for values above 3,999, medieval variants, fractions, or non-canonical spellings.