Convert Stone (US) (st (US)) to Pound-force Square Second/Foot (lbf·s²/ft) instantly.
About these units
Stone (US) (st (US))
The US stone was an informal and nonstandardized unit occasionally used in the 19th century, with no single agreed-upon value. Unlike the British stone (14 pounds), the US stone varied regionally and by trade context, typically ranging from 12 to 16 pounds, depending on the commodity and location. Farmers, butchers, and merchants sometimes used stones to weigh produce, meat, or livestock, but the lack of uniform regulation prevented it from becoming an official or widely adopted unit. Today, the US stone is entirely obsolete, but references to it appear in historical American trade documents, agricultural records, and pre-standardization weight systems. It serves as a reminder of the diversity of early American measurements before the widespread adoption of the avoirdupois pound.
Pound-force Square Second/Foot (lbf·s²/ft)
This unit is part of the British Gravitational System, where mass is defined from force rather than the other way around. It can be interpreted as an inertial mass unit, since applying 1 pound-force to it would produce an acceleration of 1 foot per second squared. Historically, before the SI system clarified the distinction between force and mass, engineering fields often used mixed systems where pounds could represent either force (lbf) or mass (lbm). The unit lbf·s²/ft was introduced to straighten out these ambiguities in dynamic calculations such as impact forces, mechanical oscillations, and safety load computations. Today, the unit survives mostly in engineering textbooks, legacy calculations, and historical documentation. It demonstrates how complex and inconsistent measurement systems once were, and why global scientific communities moved toward SI clarity.