In Roman numerals, IV represents the number 4. It is formed by subtracting 1 (I) from 5 (V) . While it is the most common way to represent the number 4 in Roman numerals, there are some cases where IIII is used instead of IV, such as on the dial plates of clocks that use Roman numerals. This convention is thought to have originated in the late 14th century when Charles V, the king of France, considered IV to be bad luck as it was created by subtracting 1 (I) from his title 5 (V) .