The proper way to express torque units is lbf·ft or N·m

The proper way to express torque units is lbf·ft or N·m

Torque =  Force * Length

This means N·m is acceptable, lbf·in is acceptable, and lbf·ft is acceptable.

ft·lbf or in·lbf is not the conventional method for expressing torque. You will not find this as an accepted expression of torque in the ASTM torque standard (ASTM E2428) or any NIST handbook. You will find several manufacturers expressing torque the improper way.

The foot-pound force (symbol:  ft·lbf) is a unit of work or energy in the Engineering and Gravitational Systems in the United States' customary and imperial units of measure. It is the energy transferred by applying a force of one pound-force (lbf) through a linear displacement of one foot.

A  pound-foot  (lbf·ft) is a unit of torque or moment of force (a pseudovector). One pound-foot is the torque created by one pound force acting at a perpendicular distance of one foot from a pivot point.

Torque is derived from the SI units of Length, Mass, and Time. The metre is the SI base unit of length. The kilogram is the SI base unit of mass. The second is the SI base unit of time.  T.

Torque Conversions Per NIST sp811

It is important to note that NIST does not currently offer torque calibration services.  A list of NMIs (National Metrology Institutes) offering torque can be found on the BIPM website here.

Morehouse currently has the second most accurate torque machine in the world. This is the most accurate machine in North America. We can achieve measurements better than 0.0025 % of applied torque from 0.5 through 1475 lbf · ft. Since NIST does not offer torque, Morehouse can provide torque measurements traceable to SI, through NPL for anyone in North America needing traceable torque measurements.

More information on our torque calibration services can be found here.

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