Drag Performance Calculator
By AssassinRacing.com

Calculate the theoretical 1/8 Mile ET, 1/4 Mile ET, 1/4 Mile Top End Speed, and Ideal 1/4 Mile Gear Ratio for a given application based on the Vehicle Weight (in pounds), Vehicle Horsepower (at the flywheel), RPM through lights (finish line), and Tire Diameter (Height) in Inches.

Assumptions: The vehicle is a car driven on concrete with tire pressures set to 30 psi. Ambient temperature is around 25º Celsius (77º Fahrenheit), no wind, good traction, and average reaction time at launch (starting line). Also include the weight of the driver and passengers and the fuel load as part of the vehicle weight.

Tech Tip:
The most accurate way to measure tire diameter is to use a tape measure and measure the actual distance (diameter) from the ground to the top of the tread of the tire. A quick way to approximate the tire diameter is to add the wheel diameter to twice the height of the tire sidewall. For example, a car with 225/40R tires has a sidewall height of 3.54" (225 mm x 40/100 is 90 mm which is 3.54"). If it has 18" wheels then the tire diameter is roughly 25" (18 + 3.54 + 3.54).

Use the 0-60 MPH Time Calculator to calculate the theoretical 0-60 Time for a given application.

Top speeds are either gear limited or drag limited. Use the Gear Ratio Speed Calculator to determine which is the case for your particular scenario. Use the horsepower calculator to find out how much horse power a car would require to run at a given speed.