Convert Stone (US) to Slug

The stone as a unit of mass has roots dating back to ancient times, where it was used in various cultures for weighing goods, with the weight of a stone varying by country and commodity. In the UK, the stone was historically used to measure items like wool, and the weight of the stone varied (ranging from 5 to 30 pounds) based on the goods being measured. The U.S. adopted a 14-pound stone in the 19th century, primarily as a way to measure body weight, though it is now largely replaced by the pound for more precise measurements. The 14-pound stone is still used informally in some areas, especially in the context of body weight.

The slug was introduced in the late 19th century as part of the foot-pound-second (FPS) system, which was developed to be more consistent with the principles of mechanics, particularly Newton's second law of motion. The term "slug" was chosen because it represented a unit of mass that would help express the relationship between force, mass, and acceleration in a way that was easier to apply in engineering and scientific calculations. The slug is used primarily in the U.S. and some engineering contexts, but it is less common in everyday measurements, where the pound is typically used for mass and weight.