Torque Converter

Torque is rotational force, the twisting effort that turns a bolt, spins a wheel, or cranks an engine. The SI unit is the newton-meter (Nm); the imperial world uses the foot-pound (ft-lb).

Key relationships:

• 1 ft-lb = 1.35582 Nm
• 1 kgf-m = 9.80665 Nm
• 1 in-lb = 0.112985 Nm

Common references:

• A car lug nut: 80–100 ft-lb (108–136 Nm)
• A spark plug: 12–18 ft-lb (16–24 Nm)
• A bicycle pedal: 30–35 Nm

These figures matter more than they look. Under-torque a lug nut and the wheel can work loose; over-torque it and you warp a brake rotor or snap the stud. That’s the whole reason torque wrenches exist, and why mechanics care about the exact number rather than “good and tight.”

The classic mix-up is torque versus power. Torque is the turning force at a given instant; power is how much work that force does over time, which depends on how fast the shaft spins. RPM ties them together:

• Power (HP) = Torque (ft-lb) × RPM ÷ 5252
• Power (kW) = Torque (Nm) × RPM ÷ 9549

That’s why a diesel can make huge torque at low RPM yet modest horsepower, while a small high-revving engine does the reverse. They’re two different questions about the same spinning shaft.