Ligne is a French word meaning line. It was in use prior to the French adaptation of the metric system in the late 1700s, and is still used by French and Swiss wristwatch makers to measure the size of a watch movement. (For example, Girard-Perregaux will introduced a new 12 ligne chronograph movement.) In this usage there are 12 ligne to one French inch. The standardized conversion for a ligne is 2.2558291 mm, and it is abbreviated with the letter L.

In the eighteenth century the term ligne came into use among German button makers, where is was used to measure the diameter of buttons. The consensus definition was that a ligne was the measurement of a round wick, folded flat. In this sense it measures 1/40th of an inch.

See also

• Horology