Torque Converter

Torque is the rotational equivalent of linear force — it measures the tendency of a force to rotate an object about an axis. In everyday terms, torque is what you apply when you use a wrench to tighten a bolt, turn a doorknob, or pedal a bicycle. The greater the torque, the more effectively the object rotates. Torque is a fundamental quantity in mechanics, engineering, and automotive design, determining how quickly an engine can accelerate a vehicle, how much load a motor can move, and how tightly a bolt can be fastened.

The SI unit of torque is the Newton-meter (Nm), defined as the torque produced by a force of one Newton applied at a lever arm of one meter. Other commonly used units include the pound-foot (lb-ft) in the imperial system, kilogram-force meter (kgf-m) in metric engineering, and the dyne-centimeter (dyn-cm) in CGS units for small-scale physics. The choice of unit depends on the engineering discipline and regional conventions.

Torque is calculated as the cross product of the position vector (lever arm) and the force vector: τ = r × F × sin(θ), where r is the distance from the axis to the point of force application, F is the force magnitude, and θ is the angle between the force and the lever arm. For forces applied perpendicular to the lever arm (the most common case), this simplifies to τ = r × F.

Understanding torque conversions is essential for automotive engineers specifying engine output, mechanics selecting the right wrench size, physicists calculating rotational dynamics, and anyone working with rotating machinery or mechanical fasteners.

All conversions in this calculator go through the SI base unit of Newton-meters (Nm). Each unit's conversion factor represents how many Nm are equivalent to one unit of that measure. The calculator multiplies the input by the source factor to convert to Nm, then divides by the target factor to get the result.

The key conversion relationships are: 1 lb-ft = 1.35582 Nm (the most common imperial-to-SI conversion), 1 kgf-m = 9.80665 Nm (based on the standard acceleration of gravity), and 1 lb-in = 0.112985 Nm (one-twelfth of a pound-foot, useful for smaller torque values). For very small torques, 1 dyn-cm = 10⁻⁷ Nm.

Torque values vary enormously across applications. A typical car engine produces 200-400 Nm (150-300 lb-ft) of peak torque, while a heavy-duty truck engine might produce 1,500-2,500 Nm (1,100-1,850 lb-ft). Electric motors in Tesla vehicles produce up to 750 Nm instantaneously, which is why electric cars accelerate so quickly — torque is available from zero RPM.

For hand tools, the torque applied to bolts varies by size: a small 1/4-inch drive socket might handle 5-25 Nm, a 3/4-inch drive impact wrench up to 2,000 Nm, and a heavy-duty lug nut wrench typically applies 100-150 Nm. Over-torquing can strip threads or break bolts, while under-torquing can lead to loosening and failure.

In physics research, torque measurements at the micro-Newton-meter scale are used in torsion pendulum experiments to measure gravitational constants, while nano-Newton-meter torques are relevant in molecular biology for understanding the forces that DNA and proteins experience during cellular processes.

This converter handles eight torque unit systems:

1. Enter the Value: Type the torque value into the input field.
2. Select the Source Unit: Choose the unit of your input from the "From" dropdown. Options include Nm, kNm, lb-ft, lb-in, kgf-m, kgf-cm, dyn-cm, and ozf-in.
3. Select the Target Unit: Choose the unit you want to convert to from the "To" dropdown.
4. Read the Result: The converted value appears immediately, and the "All Conversions" panel shows your value in every supported unit simultaneously.
5. Swap Units: Click the swap button to reverse the conversion direction.

Torque conversion is critical in automotive engineering, where engine specifications are listed in different units depending on the market. European manufacturers typically specify torque in Nm, while American manufacturers use lb-ft. Comparing engine outputs across markets requires accurate conversion, as does specifying torque converter stall speeds, clutch ratings, and differential gear ratios.

In mechanical engineering and manufacturing, bolt tightening specifications must be precise. A bolt specified in Nm must be converted to lb-ft when using an imperial torque wrench, and vice versa. Incorrect torque can lead to catastrophic failures in applications from aircraft engines to bridge construction.

Physics and engineering education requires fluency in torque unit conversion. Students learning rotational dynamics must work with SI units (Nm) in theoretical calculations while encountering imperial units (lb-ft) in practical applications and lab equipment specifications.

In industrial motor selection, torque ratings may be specified in different unit systems depending on the motor's country of origin. Converting between Nm, kgf-m, and lb-ft ensures correct motor selection for pumps, conveyors, and other rotating equipment.