Why Is V Capitalized in kV?

There are clear rules for writing unit symbols in physical units and the International System of Units (SI). The "V" in "kV" (kilovolts) is capitalized for the following reasons:

The Unit Is Derived from a Person's Name

The unit of voltage, the volt, is named in honor of the Italian physicist Alessandro Volta.

Naming Rules of the International System of Units

According to the International System of Units, if a unit name is derived from a scientist's surname, the first letter of the unit's symbol must be capitalized. Examples include:

Volt → V

Watt → W

Ampere → A

Hertz → Hz

Difference from Prefixes

"Kilovolt" (kV) is composed of the prefix "k" (meaning thousand) and the unit symbol "V" (volt).

The prefix "k" represents a factor of one thousand and must always be written in lowercase, regardless of the unit it precedes. (For example, "k" in km, kg, and kV is lowercase, while "M" for million is uppercase.)

The unit symbol "V" represents the volt and, because it is derived from a person's name, must be capitalized.