Engine Torque Calculator

How to Calculate Engine Torque

Calculating engine torque from horsepower and RPM is a fundamental task in automotive engineering. This calculator simplifies the process by using the standard formula for torque calculation.

What is the Formula?

The formula for calculating engine torque is:

\[ \text{Torque (lb-ft)} = \frac{\text{Horsepower} \times 5252}{\text{RPM}} \]

Where:

• Torque is measured in pound-feet (lb-ft)
• Horsepower is the input power of the engine
• 5252 is a constant derived from the relationship between horsepower and torque
• RPM is the engine speed in revolutions per minute

What are the calculation steps?

1. Determine the engine's horsepower output
2. Measure or specify the engine speed in RPM
3. Multiply the horsepower by 5252
4. Divide the result by the RPM
5. The final result is the engine torque in lb-ft

Example Calculation

Let's calculate the torque for an engine with 200 horsepower running at 4000 RPM:

Step 1: Identify the inputs

Horsepower = 200 hp

RPM = 4000

Step 2: Apply the formula

Torque = (200 × 5252) / 4000

Step 3: Calculate

Torque = 1050400 / 4000 = 262.6 lb-ft

Therefore, an engine producing 200 horsepower at 4000 RPM generates approximately 262.6 lb-ft of torque.

Diagram of Engine Torque Calculation

The following diagram illustrates the relationship between horsepower, RPM, and torque:

This diagram shows how torque (green curve) varies with RPM for a given horsepower. As RPM increases, torque typically decreases, assuming constant horsepower.