How do I convert lb·ft to N·m?

Multiply lb·ft by 1.35582. Example: 100 lb·ft × 1.35582 = 135.58 N·m. For quick mental math, multiplying by 1.356 is accurate to within 0.01%.

What is the difference between lb·ft and lb·in?

lb·in is pound-inches and lb·ft is pound-feet. 1 lb·ft = 12 lb·in. Fastener torque specs for small screws and bolts (M6 and under, #10 and under) are often given in lb·in or N·m to avoid fractional lb·ft values.

Why is torque measured at the crankshaft, not the wheels?

Crankshaft torque is the engine's own output before transmission, driveshaft, differential, and axle losses. Wheel torque is higher numerically (multiplied by the gear ratio) but is harder to measure directly. Most performance figures quote crankshaft torque.

Is higher torque always better?

Higher torque means more rotational force, which is useful for towing, climbing, and acceleration from rest. But torque must be matched to the speed at which it is delivered (RPM). Power = torque × angular velocity. A high-torque, low-RPM engine and a low-torque, high-RPM engine can produce the same power.

Torque Units Explained: Newton-Metres vs Pound-Feet vs Pound-Inches

Torque is a rotational force — the tendency of a force to cause rotation about an axis. It appears in fastener specifications, engine output ratings, and electric motor datasheets. This guide explains what torque units mean, how to convert between them, and the surprisingly easy mistake that can strip a bolt or damage an engine.

Published March 19, 2026

Key takeaways

Torque = Force × Lever arm length. The SI unit is the newton-metre (N·m).
1 lb·ft = 1.35582 N·m. 1 N·m = 0.737562 lb·ft.
lb·in (pound-inch) is used for small fasteners; lb·ft for larger ones and engines.
Engine torque peaks at lower RPM than horsepower — torque is what accelerates, horsepower sustains speed.
Never mix up torque and energy — both use N·m but they are physically different quantities.

What is torque?

Torque (τ) is the rotational equivalent of linear force. It is the product of a force (F) and the perpendicular distance (r) from the pivot point to the line of action of the force:

τ = F × r

The SI unit of torque is the newton-metre (N·m). A force of 1 newton applied at 1 metre from the pivot produces 1 N·m of torque. Note that N·m is also the unit of energy (the joule), but torque and energy are physically distinct — torque is a vector quantity related to rotation, not a scalar energy.

Conversion factors

Formula

1 N·m   = 0.737562 lb·ft
1 lb·ft = 1.35582 N·m
1 lb·ft = 12 lb·in
1 N·m   = 8.85075 lb·in
1 lb·in = 0.112985 N·m
1 kgf·m = 9.80665 N·m (kilogram-force metre, older engineering standard)

Automotive applications

Engine torque is the rotational force the crankshaft delivers to the drivetrain. It is what determines how quickly a vehicle accelerates from rest.

In North America, engine torque is almost always quoted in lb·ft. In Europe and Asia, N·m is standard. A typical family saloon might produce 250–350 N·m (184–258 lb·ft); a large diesel truck engine can produce 2,000+ N·m (1,475+ lb·ft).

Fastener torque specs in North American service manuals are typically in lb·ft for large fasteners (cylinder head bolts, lug nuts) and lb·in for small ones (valve cover bolts, electronics brackets). European manuals use N·m throughout.

Electric motors and torque

Electric motors are characterized by high torque at low or zero RPM — unlike internal combustion engines, which produce maximum torque in a mid-range RPM band. This is why electric vehicles feel so responsive from standstill.

Motor datasheets typically quote peak torque in N·m and continuous torque separately. Continuous torque is what the motor can sustain indefinitely without overheating; peak torque may only be available for seconds.

Torque vs energy: a common confusion

Important

Both torque and work/energy are measured in N·m, but they are not the same.

Work (energy) = Force × Distance (scalar, in joules = N·m) Torque = Force × Lever arm (vector, in N·m)

The difference is that work involves force acting along a displacement, while torque involves force acting perpendicular to a radius. Numerically 1 N·m of torque ≠ 1 J of energy unless that torque acts through 1 radian of rotation (then energy = torque × angle in radians).

Fastener torque quick reference

Formula

Typical torque specs for common fasteners (values vary by application — always consult a service manual):

Fastener               N·m          lb·ft      lb·in
M6 bolt (Grade 8.8)    10           7.4        89
M8 bolt (Grade 8.8)    25           18.4       221
M10 bolt (Grade 8.8)   49           36.1       434
M12 bolt (Grade 8.8)   86           63.4       761
Car wheel nut          90–130       66–96      792–1150
Spark plug (14mm)      20–30        15–22      177–266
Engine cylinder head   varies — always follow torque sequence and spec in service manual

Conversion reminder:
1 lb·ft = 1.35582 N·m
1 N·m   = 0.737562 lb·ft
1 lb·ft = 12 lb·in

When to use N·m vs lb·ft vs lb·in

Use N·m when: following European or Asian service manuals, working in a scientific or SI engineering context, or reading electric motor datasheets. N·m is unambiguous and internationally consistent.

Use lb·ft when: following US automotive service manuals, specifying engine torque for a US audience, or using a US torque wrench calibrated in lb·ft. US spec manuals typically use lb·ft for all fasteners above about 5 lb·ft.

Use lb·in when: working with small fasteners where lb·ft values would be fractional. Electronics brackets, valve cover bolts, and accessory bolts often specify 25–100 lb·in (2–8 lb·ft). Using lb·in avoids the awkward '0.5 lb·ft' notation.

Practical tip: many quality torque wrenches display both N·m and lb·ft on the scale. When in doubt, convert and use whichever unit the specification uses — do not convert and risk rounding errors on critical fasteners.