One of the most common questions we are asked when customers call us about our Performance Software, is “What is the difference between horsepower and torque and what does that mean to me?” This is undoubtedly one of the most brought up questions in automotive tuning history.

This article is meant to be for informational purposes only, as we by no means claim to be an absolute authority on the subject. We have done our best to sum up the knowledge we have, present it in a nice format, and then leave the facts for you to talk about amongst yourselves to decide what you feel is the more important of the two :Horsepower or Torque.

I’ll start with the basic definitions, and then explain each of them in further detail.

Horsepower Definition: How much work is done over what period of time.

Many years before Mercedes Benz was producing engines with over 450 horsepower, a man named James Watt made some observations, and concluded that an average horse could lift a 550 pound weight one foot in one second, thereby performing work at the rate of 550 foot pounds per second, or 33,000 foot pounds per minute, for an eight hour shift, more or less. Watt published those observations, and stated that 33,000 foot pounds per minute of work was equivalent to the power of one horse, or, our topic of the day, one horsepower.

To further explain, let us look at the following scenario. If you have a one pound weight bolted to the floor, and try to lift it with one pound of force (or 10, or 50 pounds), you will have applied force and exerted energy, but no work will have been done (hence, you have zero horsepower.) If you unbolt the weight, and apply a force sufficient to lift the weight one foot, then one foot pound of work will have been done. If that event takes a minute to accomplish, then you will be doing work at the rate of one foot pound per minute. If it takes one second to accomplish the task, then work will be done at the rate of 60 foot pounds per minute, and so on.

Torque Definition: The measure of the force applied to an object to produce rotational motion, usually measured in foot-pounds.

Torque literally refers to the turning or twisting force of an engine. An engine may be very powerful, but if it has little torque then that power may only be available over a very high and limited rev range, making it of limited use to the driver. An engine with more torque - even if it has less power – often proves to be much quicker on the track, as the power is available over a far wider rev range and hence more accessible.

To give a slightly more technical explanation, one foot pound of torque is the twisting force necessary to support a one pound weight on a weightless horizontal bar, one foot from the fulcrum.

Imagine, this one pound weight, one foot from the fulcrum on its weightless bar. If we rotate that weight for one full revolution against a one pound resistance, we have moved it a total of 6.2832 feet (Pi * a two foot circle), and, incidentally, we have done 6.2832 foot pounds of work.

Now, it’s important to understand that nobody on the planet ever actually measures horsepower from a running engine. What we actually measure (on a dynamometer) is torque, expressed in foot pounds (in the U.S.), and then we *calculate* actual horsepower by converting the twisting force of torque into the work units of horsepower.

OK. Remember Watt? He said that 33,000 foot pounds of work per minute was equivalent to one horsepower. If we divide the 6.2832 foot pounds of work we’ve done per revolution of that weight into 33,000 foot pounds, we come up with the fact that one foot pound of torque at 5252 rpm is equal to 33,000 foot pounds per minute of work, and is the equivalent of one horsepower. If we only move that weight at the rate of 2626 rpm, it’s the equivalent of 1/2 horsepower (16,500 foot pounds per minute), and so on. Therefore, the following formula applies for calculating horsepower from a torque measurement: