Calculate HP For Speed 
Air Drag Coefficients and Frontal Area Calculation
Coefficient of DragThe aerodynamic "features" of a vehicle in motion are reflected in its drag coeficient values. Low coefficients indicate low air resistance. The following chart list some ranges for various vehicles, which will suffice when actual measured values are not available:
Vehicle Drag Coefficient Description Low Medium High  Experimental 0.17 0.21 0.23 Sports 0.27 0.31 0.38 Performance 0.32 0.34 0.38 60's Muscle 0.38 0.44 0.50 Sedan 0.34 0.39 0.50 Motorcycle 0.50 0.90 1.00 Truck 0.60 0.90 1.00 TractorTrailer 0.60 0.77 1.20
Calculation of Frontal AreaFrontal area represents the front projection area of the vehicle. If one takes a picture of a vehicle, it is the area included in the outline. Use the following to calculate:1. Calculate the area of a rectangle which would encompass the front of the vehicle (multiply width by the height). For motorcycles, use the handlebar width (to a maximum width of 30 inches) and a height consisting of seat height plus an estimated "seat to helmet" height. 2. Adjust the figure obtained above for areas not included, such as top rounded corners, etc. Typical adjusting values are 85 percent for cars, 70 percent for motorcycles, and 100 percent for trucks. 

