Torque Converter

Torque is force times distance from the pivot: τ = F × r. Its SI unit, the newton-meter, is the torque from one newton acting at one meter. Every conversion here pivots through the newton-meter: first multiply into N-m, then divide out to the target unit, so all 9 units stay consistent.

The factors are high-precision standards: 1 lbf-ft = 1.35581795 N-m (from the exact 1959 yard and pound definitions), 1 kgf-m = 9.80665 N-m (exact standard gravity), 1 lbf-in = 0.112984825 N-m. Results show up to 10 significant digits, more than enough for any wrench setting.

Newton-meters rule science, international engineering, and most car manuals outside the US. Pound-feet dominate US automotive specs: lug nuts, head bolts, spark plugs. Pound-inches cover small fasteners where foot-pounds would be clumsy decimals.

Kilogram-force meters survive in older metric machinery and some Asian specs; kilonewton-meters in heavy industry and structural work; dyne-centimeters in laboratory CGS contexts. Picking the wrong unit family is how a 140 N-m lug nut spec becomes a dangerous 140 lbf-ft guess, so convert deliberately.

Three conversions cover most real-world needs. 1 N-m = 0.737562 lbf-ft, so multiply newton-meters by 0.74 for a quick mental estimate. 1 lbf-ft = 1.35582 N-m going the other way. And 1 lbf-ft = 12 lbf-in exactly, the whole-number bridge between the two US units.

Worked example: a manual calls for 140 N-m on wheel lug nuts and your wrench reads pound-feet. 140 × 0.737562 = 103.26 lbf-ft. Setting 103 on the wrench nails the spec; guessing 140 would over-torque by 36 percent.

Torque and force share no units, even though both describe push. Force is measured in newtons or pounds-force; torque is force at a distance, newton-meters or pound-feet. Saying an engine makes 400 pound-feet of torque is not saying it pushes with 400 pounds.

The confusion bites with the similar names: a pound-foot of torque versus a foot-pound of energy are dimensionally identical but conceptually different. For pure force conversions (newtons to pounds-force), use the force converter instead.

Under-torqued bolts loosen under vibration; over-torqued bolts stretch, strip, or snap. Wheel lugs, cylinder head bolts, and brake calipers all carry torque specs for this reason, and the spec's unit is part of the spec.

A torque wrench is only as honest as its calibration, so convert the spec to the wrench's own unit rather than converting the wrench reading in your head mid-job. When the manual gives a range, aim for the middle; when it gives angle-plus-torque (torque-to-yield), follow the angle step exactly.

In a spreadsheet, keep one column in N-m as the canonical value and convert outward with the factors above; that avoids compounding rounding across chained conversions. In code, store the factor constants at full precision (1.35581795, not 1.36) and round only for display.

Watch for the hyphen confusion: some datasets write lb-ft, others lbf-ft or ft-lb. They all mean the same torque unit here. And never mix torque units with energy units in the same column, even though both reduce to newton-meters dimensionally.