How To Calculate Your Horsepower
Horsepower is a way to measure the power output of an engine or motor. There are different formulas to figure out the amount of horsepower your engine is making. For this calculator, you have the option to use the Elapsed Time Method, the Trap Speed Method, or the RPM & Torque Method.
Of course, the best method to figure out how much power your vehicle is making is using a dynamometer. Or “dyno” as it’s usually called. A dynamometer is a device that measures the torque and rotational speed (RPM) of an engine, motor or other rotating prime movers. It allows instantaneous power to be calculated and usually displayed as kW or BHP.
If you don’t have access to a dyno, our engine horsepower calculator will at least give you a rough estimate.
Caution: Do not attempt to find your elapsed quarter-mile time on public streets or highways. Driving over the speed limit is illegal and dangerous.
Our Engine Horsepower Calculator Uses These Methods
The Elapsed Time method
This method estimate horsepower by using the weight of the vehicle and the time it took that vehicle to travel a quarter-mile.
The formula for the elapsed time method:
horsepower = weight ÷ (time ÷ 5.825)3
The Trap Speed method
This method uses the weight of the car and the speed at which the vehicle completed the quarter-mile run.
The formula for the trap speed method:
horsepower = weight × (speed ÷ 234)3
The RPM & Torque Method
Using the RPM and torque of the motor, it’s possible to estimate the horsepower. This information is found online or your vehicle documentation.
So What Is Horsepower?
Where does the term come from? And what is a horsepower anyway? James Watt had invented the steam engine but was having trouble convincing skeptics to ditch their horses and buggies and buy his product. He had the brilliant idea to create a formula to prove the efficiency of his invention over the horse. So, Watt, had a horse walk in circles to turn a grindstone in a mill. He multiplied the distance the horse walked in one minute by the weight he thought it could pull, 180 pounds. His estimate was shockingly close. Watt then divided by time to find the force and distance per minute. That number equals one new unit of measure, which Watt called horsepower.
What else does one horsepower equal?
- A burst on a bicycle. In a flat-out sprint, the average cyclist can eke out one single horsepower. Professionals peddlers can make around 2HP.
- A drip coffee maker. We measure electricity in Watts named after our friend James Watt, of course. 746 Watts, which is enough to power a standard drip coffee maker, equals one horsepower.
- A big pasta party. Heat is another form of energy. One horsepower is equal to 2545 BTU or British Temperature Units. In a perfect world where no energy is lost, that’s enough to boil 2.2 gallons of room temperature water and cook 14 servings of pasta.
What’s the most horsepower in a single-engine?
Understanding Types Of Horsepower
Horsepower is one of the more confusing things in the world of cars. Whether it’s horsepower vs. wheel horsepower, Gross BHP vs. Net BHP, it’s easy to get it wrong. So here’s an easy breakdown.
There are three main types, horsepower, brake horsepower, and wheel horsepower.
Horsepower or Indicated Horsepower
Simply a theoretical calculation of the maximum amount of work your engine can do without anything like friction affecting it. A device called an engine indicator measures the theoretical power by creating a plot between the pressure and volume curves inside the cylinders. You’ll very often see car manufacturers refer to their cars in horsepower as it’s the highest number they can achieve.
Is the actual power measured at the crankshaft. It includes the losses caused by engine friction, but before any losses of the drivetrain and gearbox. This is where a lot of confusion comes in because within BHP (brake horsepower)there are two ways it can be measured, Gross BHP or Net BHP. Gross BHP measures power at the flywheel, but with no engine ancillaries connected. Net BHP takes parasitic parts into account.
If you were to go back to America 50 years ago, engines were often tested and advertised in Gross PHP, making figures much higher than the rest of the world. So to correct this in 1972, the SAE net standard was set to make sure that all engines were measured using Net BHP. This requires including the approximate accessories that are added in production.
Effective horsepower, commonly called Wheel Horsepower, is measured at the wheels. It takes into account all engine and drivetrain losses along the way. This is usually done by running the car on the dynamometer.
Our engine horsepower calculator gives you a way to measure the approximate Wheel Horsepower of your vehicle.