Article — Nm to ft-lb Converter
Nm to ft-lb: convert torque between Newton-meters and foot-pounds
One Newton-meter equals 0.737562 foot-pounds. One foot-pound equals 1.35582 Newton-meters. Both numbers are exact, derived from the 1959 international definitions of the metre, foot, and pound-force. Service manuals split the difference by country — European and Japanese in Nm, US in ft-lb — and getting the conversion wrong by 35% (the difference between 100 Nm and 100 ft-lb) is how wheels come off and head bolts strip.
The calculator at the top of this page handles both directions and includes the common automotive torque ranges as quick picks. The article below explains why torque matters, where the numbers come from, and the most common torque specs you will run into.
What is torque?
Torque is rotational force — the twisting effort applied around an axis. When you tighten a bolt, you apply torque to it. When an engine drives the crankshaft, it produces torque. The standard unit in the SI system is the Newton-metre (Nm or N·m), defined as one newton of force applied at a distance of one metre from the rotation axis.
In the imperial system the equivalent is the foot-pound (ft-lb), one pound-force applied at one foot from the axis. The two units measure the same physical quantity, scaled by the difference between metric and imperial.
The Nm to ft-lb formula
To convert Newton-metres to foot-pounds, multiply by 0.737562. To convert foot-pounds to Newton-metres, multiply by 1.35582:
Nm × 0.737562 = ft-lbft-lb × 1.35582 = NmNm × 0.74 (0.3% error, fine for shop work)ft-lb × 1.36 (reverse shortcut)The factor 0.737562 is not rounded. It is built from two definitions — one newton equals 0.224809 pound-force, and one metre equals 3.28084 feet — multiplied together. The reciprocal (1.35582) comes out exactly the same way.
Common torque conversions
The values most frequently looked up by mechanics, DIYers, and engineers:
- 10 Nm = 7.38 ft-lb (small fasteners, valve covers)
- 25 Nm = 18.44 ft-lb (spark plugs, sensors)
- 50 Nm = 36.88 ft-lb (oil drain plug on most engines)
- 100 Nm = 73.76 ft-lb (typical passenger-car lug nut)
- 150 Nm = 110.63 ft-lb (heavier vehicle lug nut)
- 200 Nm = 147.51 ft-lb (light truck lug nut)
- 300 Nm = 221.27 ft-lb (heavy-duty truck wheel)
- 500 Nm = 368.78 ft-lb (final stage of head-bolt sequence on V8)
Torque specs by fastener
Every bolt on a vehicle has a manufacturer-specified torque. Stripping or under-torquing has expensive consequences. Common ranges in both units:
The Volvo D17 truck engine generates roughly 3,800 Nm (2,802 ft-lb) of peak torque. That is enough force to spin a 1-metre lever arm with 380 kilograms of weight on the end. For comparison, a Honda Civic engine peaks around 175 Nm — more than 20 times less torque, though it spins much faster to produce useful horsepower.
Torque vs. energy: same units, different things
This trips up engineering students every year. Newton-metres (N·m) and joules (J) have identical dimensional units — force times distance — but they refer to different physical quantities.
Torque is a vector. It represents rotational force around an axis and has a specific direction (clockwise or counter-clockwise). You apply torque to a bolt; you do not apply joules.
Energy (or work) is a scalar. It represents the result of applying force across a distance — the work done. You measure engine output in joules per second (watts) but engine torque in Newton-metres.
By convention, torque is written N·m with the centre dot, and energy is written J. The convention exists precisely so the two are not confused, even though dimensionally they are interchangeable.
Under-torque vs. over-torque
Both errors are dangerous, in different ways. Under-torquing a fastener leaves it loose. Over-torquing strips the threads, snaps the bolt, or warps whatever the bolt is clamping.
Lug nuts under-torqued by even 25% can work loose over a few hundred miles of driving, leading to wheel separation at highway speed. Over-torqued by 25% they strip the wheel stud or warp the brake rotor on the next thermal cycle. Always use a calibrated torque wrench and the manufacturer's spec — not the impact gun's setting.
Critical fasteners use specific torque-and-angle sequences. Modern cylinder head bolts, for example, are tightened to a base torque (say 30 Nm), then turned an additional 90° in a specific bolt order, then a further 90°. This "torque-to-yield" method gets the bolt to the optimal clamp force without relying on torque alone.
Inch-pounds and other torque units
Beyond Nm and ft-lb, two smaller units appear in service manuals:
Inch-pounds (in-lb). One-twelfth of a foot-pound. Used for very small fasteners — interior trim, electronics, sensitive sensors. 1 Nm = 8.85 in-lb. A typical sensor housing torques to 5–10 in-lb.
Kilogram-force metre (kgf·m). Old metric unit, still seen in vintage Japanese service manuals. 1 kgf·m = 9.80665 Nm. Mostly obsolete but worth recognising if you work on classic motorcycles or old Japanese cars.
The Saturn V rocket's F-1 engine turbopump produced about 70,000 newton-metres of torque at the shaft — roughly the rotational force needed to spin a 100,000 kilogram weight on a 1-metre lever. The engine had to be rebuilt between every test fire because the forces involved tore the turbopump bearings apart.
Common torque-conversion mistakes
Treating Nm and ft-lb as if they are close. They are not. 100 Nm is 73.76 ft-lb — a 35% gap. Plugging 100 ft-lb into a 100 Nm spec over-torques by 35% and almost certainly strips the fastener.
Using a torque wrench that was dropped. Mechanical torque wrenches drift out of calibration after impacts or after being stored at high tension. Storage at the lowest setting and an annual calibration check are standard shop practice.
Reading the impact gun setting as "torque." Impact wrenches do not deliver a precise final torque. They deliver enough rotational energy to spin the nut down quickly. Final torque always needs a click-type or beam torque wrench.
Ignoring the angle. Torque-to-yield specs combine a base torque and an angle (for example, "50 Nm, then 90°"). Only doing the torque step under-clamps the joint. The angle step is what brings the bolt to its working tension.