Question 1

What is the formula for torque?

Accepted Answer

The torque formula is T = F x r x sin(theta), where T is torque in Newton-meters (Nm), F is the applied force in Newtons (N), r is the lever arm length (distance from the pivot point) in meters, and theta is the angle between the force vector and the lever arm. When force is applied perpendicular (90 degrees), sin(90) = 1 and the formula simplifies to T = F x r.

Question 2

How do I calculate torque in Nm?

Accepted Answer

To calculate torque in Newton-meters: T = F (Newtons) x r (meters) x sin(angle). For example, applying 100 N force at the end of a 0.5 m wrench at 90 degrees: T = 100 x 0.5 x sin(90) = 100 x 0.5 x 1 = 50 Nm. If the force is not perpendicular, multiply by sin of the angle between force and lever.

Question 3

What is the difference between torque and moment?

Accepted Answer

Torque and moment are both calculated as T = F x r x sin(theta) and are essentially the same concept mathematically. In engineering, moment typically refers to the tendency of a force to cause rotation about a point in a static context (structural analysis), while torque specifically refers to rotational forces in dynamic systems like engines, motors, and rotating shafts. The units (Nm or ft-lb) are identical.

Question 4

How do I convert torque from Nm to ft-lb?

Accepted Answer

To convert Newton-meters (Nm) to foot-pounds (ft-lb): divide by 1.35582. So 100 Nm = 100 / 1.35582 = 73.76 ft-lb. To convert ft-lb to Nm: multiply by 1.35582. To convert Nm to inch-pounds (in-lb): multiply by 8.8507. These conversions are used frequently when working with automotive torque specs given in different unit systems.

Question 5

What is the torque of a wrench at 90 degrees?

Accepted Answer

When a wrench is used at 90 degrees (force applied perpendicular to the handle), torque is maximized: T = F x r. For a 0.3 m (about 12 inch) wrench with 200 N (about 45 lb) applied force: T = 200 x 0.3 = 60 Nm = 44.3 ft-lb. Applying force at any other angle reduces torque by the factor sin(theta), which is why pulling a wrench handle straight perpendicular gives the most torque.

Question 6

How does lever arm length affect torque?

Accepted Answer

Torque is directly proportional to lever arm length. Doubling the lever arm length doubles the torque for the same applied force. This is why longer wrenches produce more torque, why door handles are placed far from the hinge, and why steering wheels have a specific radius. A 0.5 m lever produces twice the torque of a 0.25 m lever when the same force is applied.

Question 7

What is a typical engine torque in Nm?

Accepted Answer

Typical engine torque values: Small car engines (1.0-1.6L) produce 100-180 Nm. Mid-size car engines (2.0-2.5L) produce 200-350 Nm. Performance sports cars can produce 400-700 Nm. Large truck diesel engines typically produce 800-2000 Nm. Electric motors often produce maximum torque instantly from 0 rpm, with Tesla Model S producing about 900 Nm. Torque specs for cylinder head bolts, lug nuts, and other fasteners are given in Nm or ft-lb in service manuals.

Question 8

What is the relationship between torque, power, and RPM?

Accepted Answer

Power (watts) = Torque (Nm) x Angular velocity (rad/s) = Torque x 2 x pi x RPM / 60. In horsepower and RPM: HP = Torque (ft-lb) x RPM / 5252. This means at low RPM, the same power requires more torque; at high RPM, less torque is needed for the same power. Diesel engines produce high torque at low RPM; petrol sports engines produce high power at high RPM with lower peak torque.

Question 9

How do I calculate torque for tightening bolts?

Accepted Answer

Bolt torque specs are provided by manufacturers in Nm or ft-lb. For example, wheel lug nuts on a typical passenger car require 100-130 Nm (75-95 ft-lb). To achieve a specified torque with a torque wrench: set the wrench to the required value, apply force until the wrench clicks or the indicator reaches the mark. Never exceed the specified torque as it can stretch or break the bolt or damage threads.

Question 10

What is the unit of torque?

Accepted Answer

The SI unit of torque is the Newton-meter (Nm). Other common units are foot-pound (ft-lb or lb-ft) used in the US, inch-pound (in-lb) for smaller fasteners, and kilogram-force-meter (kgf-m) used in some older references. 1 Nm = 0.7376 ft-lb = 8.8507 in-lb = 0.1020 kgf-m. The unit Nm is dimensionally the same as Joules (unit of energy) but torque is not energy - the distinction is in the geometric context.

Angle (θ)	sin(θ)	Torque (200N, 0.3m)	Efficiency
0°	0.000	0 Nm	0% — no rotation
30°	0.500	30 Nm	50%
45°	0.707	42.4 Nm	70.7%
60°	0.866	52 Nm	86.6%
90°	1.000	60 Nm	100% — maximum
120°	0.866	52 Nm	86.6%
150°	0.500	30 Nm	50%
180°	0.000	0 Nm	0% — no rotation

From	To Nm	To ft-lb	To in-lb
1 Newton-meter (Nm)	1.000	0.7376	8.8507
1 Foot-pound (ft-lb)	1.3558	1.000	12.000
1 Inch-pound (in-lb)	0.1130	0.0833	1.000
1 kgf·m	9.8067	7.2330	86.796

Application	Typical Torque	Notes
Wheel lug nuts (passenger car)	100–130 Nm	74–96 ft-lb
Cylinder head bolts	70–110 Nm	Per manufacturer spec
Spark plugs	20–30 Nm	15–22 ft-lb
Bicycle stem bolts	5–6 Nm	44–53 in-lb
Electric motor (small, 100W)	0.3–1 Nm	At rated RPM
Car engine (2.0L)	200–300 Nm	Peak at ~2000 RPM
Diesel truck engine	800–2000 Nm	High torque at low RPM

Torque
Calculator

Sources & Methodology

How to Calculate Torque — Formula and Examples

The Torque Formula

Why Angle Matters in Torque Calculations

Torque Unit Conversions

Common Torque Specifications in Engineering

Real-World Applications of Torque

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