Torque Converter

Torque units evolved alongside the same measurement traditions that produced today's force and length units. The newton-meter (N·m) is the SI unit, built directly from the definition of torque as force times lever-arm distance (τ = rF): a 1 N force applied 1 m from the pivot produces 1 N·m of torque. The pound-foot (lb·ft) is the standard US customary unit and dominates American automotive specs, engine ratings, and torque-wrench markings. The pound-inch (lb·in) is simply a finer-grained version of the pound-foot — 12 lb·in per lb·ft — used wherever the torque values involved are too small to express conveniently in feet, such as small machine screws, electronics assembly, and precision instruments. The kilogram-force meter (kgf·m), like the kilogram-force itself, is a gravity-dependent metric unit that predates full adoption of the SI newton and still appears on older European and Asian torque wrenches, motorcycle service manuals, and industrial equipment.

All conversions in this calculator route through the newton-meter as a common base unit. To convert any value, it is first multiplied by that unit's newton-meter-equivalent factor, then divided by the target unit's factor. The key factors are: 1 lb·ft = 1.35582 N·m (derived from the pound-force and the foot), 1 lb·in = 0.112985 N·m (the same pound-force over a one-inch lever arm, or 1/12 of a lb·ft), and 1 kgf·m = 9.80665 N·m (derived directly from standard gravity, g = 9.80665 m/s², applied over a one-meter lever arm). Because lb·ft, lb·in, and kgf·m all ultimately trace back to a force unit multiplied by a length, converting between them and N·m is always a simple linear multiplication — there's no offset or non-linear term to worry about, unlike temperature conversions.

Newton-meters dominate SI-based engineering specs, European and Asian vehicle manuals, and most scientific and industrial torque ratings outside the US. Pound-feet is the default unit on US automotive spec sheets — engine torque ratings, lug nut and wheel bolt specs, and most torque wrenches sold in North America are marked in lb·ft. Pound-inches take over wherever the torque value is small enough that lb·ft would require awkward fractions: consumer electronics screws, small engine components, and precision instrument fasteners are almost always specced in lb·in. Kilogram-force meters persist on older or imported equipment — motorcycle and small-engine service manuals from Japan and Europe, and industrial machinery predating full metric-SI standardization, frequently list torque specs in kgf·m, making conversion to N·m or lb·ft a routine task for technicians working across import brands.