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Mistake guide

Confusing N·m and lb·ft

A torque of 100 N·m equals 100 lb·ft.

01Assumption

A torque of 100 N·m equals 100 lb·ft.

02Actually

100 N·m is about 73.76 lb·ft. The factor from lb·ft to N·m is 1.3558179483314003.

03Why

Torque is force times lever arm, so every unit contains a length unit. For lb·ft the length is measured in feet, for N·m in metres. Because the numbers sit in a similar range, the error is not obvious when estimating.

04Check

Before applying a torque wrench, check its scale and convert if necessary rather than interpolating between scales. A difference of about 36 % is large enough to overload or underload a joint.

Matching conversions

Newton metre to Pound-footN·m → lb·ftTorquePound-foot to Newton metrelb·ft → N·mTorqueNewton metre to Kilogram-force metreN·m → kgf·mTorquePound-inch to Newton metrelb·in → N·mTorque

Matching tables

TableTorque: N·m, lb·ft and kgf·m

Unit family: Torque

Sources

BIPM SI BrochureSI base units, prefixes and official SI context.NIST Guide to SI Appendix BNIST conversion-factor method and non-SI factors.
When not to use

Do not use as the sole basis for official, medical, safety-critical or contractual decisions.

Citation

Citation note: UnitCloud, mistake guide, sources reviewed: September 2026. Source basis: BIPM SI Brochure · NIST Guide to SI Appendix B.