# Motor Torque Calculation Formulas

January 27, 2012

Motor torque calculation is useful for the mechanically minded car enthusiast, not only to assist in engine tuning, but to identify performance points that may need improvement as well. Torque calculation formulas are not for the everyday motorist. These formulas are best reserved for the die hard tuner or mechanic to get an idea on how well a particular engine may perform. This will also give them an idea on how to further improve engine performance, and how the motor may respond to additional modifications.

#### Braking Torque

The required braking torque of a motor may be calculated using this formula:

#### T=5252 x HP / rpm

Where:

T = Full load motor torque (expressed in lb-ft)

5252 = constant

HP = horsepower of the motor

rpm = revolutions per minute or engine speed

#### Calculating Torque

Torque is the force needed to produce rotation and consists of a force acting on a certain distance. Torque is expressed in pound-feet (lb-ft) or NM (Newton meters.)

To calculate torque, the following formulas should be considered:

#### 1. T = F x D

Where:

T = torque (lb-ft)

F = force (lb)

D = distance (ft)

2. T = 5252 x HP / RPM (if horsepower is known.)

#### Calculating Horsepower

Engine horsepower is the actual work done over time, and used as a comparison of performance among new or older model cars. When manufacturers release a new car, they often boast of increased horsepower in the engine that translates to more driving fun. Remember that an engine is not all about horsepower alone, as torque is a determining factor on engine power, performance and efficiency as well.

Horsepower is determined by the formula:

HP = rpm x T (torque) / 5252

Where:

HP = horsepower

T = torque

5252 = constant

All of these may seem complex, but the formulas given are a fun way to experiment with the torque and horsepower figures of your car.