Pound-force (lbf) is the standard imperial unit of force in the United States, defined as the gravitational force exerted on one pound of mass at sea level. It appears in bolt tension ratings, material testing, and mechanical engineering specifications throughout North America. One pound-force equals approximately 4.448 newtons.

Kilogram-force (kgf) is a non-SI unit defined as the gravitational force on one kilogram of mass at standard gravity, equal to exactly 9.80665 newtons. It is commonly used in some engineering fields and in countries transitioning from metric technical units to SI. One kilogram-force equals approximately 2.205 pound-force.