What is the rule for converting Roman numerals?

The rule for converting Roman numerals is based on adding and subtracting each numeral depending on its position relative to other numerals. In Roman numeral notation, when a smaller numeral appears before a larger one, it indicates that you should subtract the smaller from the larger. Conversely, when a smaller numeral appears after a larger one, you add its value to the larger numeral. For example, VI represents 6 because V (5) followed by I (1) implies addition, whereas IV represents 4 since I (1) precedes V (5), indicating subtraction. This fundamental principle of position and the relationship between the numerals guides the correct interpretation of Roman numerals.

The other approaches are not aligned with traditional Roman numeral conventions. For example, converting numerals directly to decimal and multiplying does not reflect how Roman numerals function. Summing only smaller numerals misrepresents the addition and subtraction rules, and simply counting total symbols overlooks the specific values and their interrelations within the numeral system.