Roman Numeral Arithmetic

To add two Roman numerals, each is first converted to its Arabic (integer) value, the numbers are added, and the sum is converted back to a Roman numeral. For example, XIV (14) + VII (7) = XXI (21).

The first Roman numeral is converted to its integer value, the second is subtracted from it, and the result is displayed as a Roman numeral. Note: if the result is zero or negative, it cannot be represented as a Roman numeral, and an error will be shown.

The tool accepts standard Roman numerals using the letters I, V, X, L, C, D, and M, representing values from 1 to 3,999 (e.g., MMMCMXCIX). Lowercase letters are automatically converted to uppercase.

The Roman numeral system has no symbol for zero or negative numbers. If the subtraction yields a value less than 1, the tool will alert you that the result cannot be expressed in Roman numerals.

Symbols are placed from left to right in decreasing value. If a smaller value precedes a larger one, it is subtracted (e.g., IV = 4). You cannot repeat V, L, or D, and I, X, C, M can be repeated up to three times. For numbers above 4,000, a bar over a symbol multiplies it by 1,000, but this tool currently supports the basic 1–3,999 range.

No, the Romans did not have a symbol for zero. They used the word nulla (meaning “none”) in some contexts, but it was never part of the numeral system. Therefore, calculations resulting in zero cannot be shown.