Horsepower from 1/4 Mile Time & Speed (ET/MPH) CalculatorUse the horsepower calculator below to find out a rough estimate of what kind of horsepower a vehicle is making by entering in its quarter mile time or mile per hour. ET Method |Trap Method Vehicle Weight With Driver :Quarter Mile Elapsed Time : Quarter Mile Trap Speed : Please note that this is an approximate figure. Do not rely on this as 100% accurate. These methods are usually very close to a Dynojet dyno, given near perfect driving. If you want to know your actual horsepower, you will have to visit a dyno.