How to Calculate Horsepower by ET
- 1). Measure the time it takes for your car to travel a quarter of a mile, starting from a stand-still. You should try to achieve your fastest time with the car's quickest acceleration. You should perform the test several times and select the best ET, measured in seconds.
- 2). Measure the weight of your car, in pounds, as it was when performing the quarter-mile tests, which means the driver should be included in the measurement. If you do not have access to a vehicle weight scale, you can reference the vehicle weight from the manufacturer's specifications and add your own weight. The specifications should be in the manual or printed on a sticker on the inside door panel.
- 3). Use the formula:
Horsepower = Weight / (ET / 5.825)^3
(The notation "^3" means to cube the figure in the preceding parenthesis.)
As an example, suppose you had a 3,800 pound vehicle that ran a quarter-mile in 11.5 seconds:
Horsepower = 3800 / (11.5 / 5.825)^3
Horsepower = 3800 / (1.97)^3
Horsepower = 3800 / 7.65
Horsepower = 497 hp
