For those of you who might not know how to work this H.P. calculator, click the "try again" button to restart the process. Type in your vehicles total weight with you in it. (There are many websites that have your vehicle weight listed on them.) Then type in the E.T. (elapsed time) that is the time that it took you and your vehicle to travel the distance of 1/4 mile. Then type in the Trap Speed, the MPH/speed that you got when you passed the 1/4 mile finish line mark.