Engine Torque Calculator

In mechanics and automobiles, understanding engine torque plays a significant role. It’s the twisting force causing rotation, the rotational force exerted by the crankshaft. Fundamentally, torque measures a motor’s ability to perform work or move the vehicle forward and is typically measured in foot pounds. This article will delve into how to calculate engine torque, a topic that’s crucial yet often misunderstood.

Torque and Horsepower: A Close Relationship

Torque can be calculated using the engine’s angular velocity in revolutions per minute (RPM) and the power in horsepower. If you need help finding the power output of your motor, you can try the Engine Horsepower Calculator.

The correlation between horsepower, torque, and RPM is beautifully intertwined. For those keen on crunching the numbers, the formula for engine torque is:

torque = (horsepower × 5,252) ÷ rpm

The number 5,252 in the formula is not just arbitrary—it’s the RPM at which horsepower and torque cross over on a graph showing the values at various RPMs.

Let’s Break It Down: An Example

To better understand how to calculate engine torque from RPM, let’s run through a quick example. Suppose we have an engine with 350 horsepower at 5,000 RPM.

First, we insert the values into the formula:

torque = (350 × 5,252) ÷ 5,000

This calculation results in:

torque = 1,838,200 ÷ 5,000

Finally, we get:

torque = 368 ft-lb

This means that the engine produces a torque of 368 foot-pounds.

Engine Torque Formula

Another popular method to determine the engine torque involves the engine force (lbf) and the crankshaft diameter (ft). Here’s the formula:



  • Te is the Engine Torque (lbf-ft)
  • Fe is the engine force (lbf)
  • Dc is the crankshaft diameter (ft)

Essentially, to calculate the engine torque, you need to multiply the engine force by the crankshaft diameter.

Practical Examples for Clarity

Let’s illustrate with two example problems to outline how to calculate the engine torque using the engine force and the crankshaft diameter.

Example Problem #1:

Engine Force (N)Crankshaft Diameter (m)

In this scenario, we calculate the engine torque as follows:

Te = 65 * 75 = 4875 (N-m)

Example Problem #2:

Engine Force (N)Crankshaft Diameter (m)

Using the same formula, we get:

Te = 900 * .8 = 720 (N-m)

These examples illustrate how different variables can impact engine torque, which in turn affects the power and performance of a vehicle. This understanding is especially vital when trying to calculate torque from RPM without power.

Important Tools

While mathematical formulas and hand calculations are informative, sometimes you need quick answers. That’s where tools like a torque to HP calculator, RPM to HP calculator, or an RPM to NM calculator can come in handy.

For example, if you want to convert different fuel flow rates like lb/hr to cc/min, you can use the lb/hr to cc/min Converter. Or perhaps you want to determine the minimum size of carburetor your engine needs; in this case, the Carburetor CFM Calculator is your friend.

Understanding the torque-to-power formula and how to calculate engine torque can give you a deeper appreciation of your vehicle’s inner workings. It provides a glimpse into the symphony of mathematics, engineering, and physics that allow our vehicles to transport us from point A to point B. So next time you put the pedal to the metal, remember the torque that makes it all possible.

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