SuperMotors Calculators

These calculators can be used to calculate relationships between various attributes involving vehicles. For most of the calculators, you can fill in all but one of the values and click the "calculate" button to have the last field determined for you. Note: These calculators are estimates only! They should not be used as hard evidence.

The following calculators are available on this page:

• Estimated horsepower (uses weight, trap speed, and horsepower)
• Estimated torque (uses horsepower, RPM, and torque)
• Estimated ET and trap speed (uses weight, horsepower, eT, and trap speed)
• Adjusted ET based on altitude (uses old ET, elevation, and new ET)
• Calculating CFM (uses engine size, RPM, and volumetric efficiency)
• Finding engine bore and stroke or displacement (uses bore, stroke, number of cylinders, and displacement)
• Converting between liters and cubic inches (uses displacement in L or ci)
• Total effective engine compression (uses naturally aspirated engine compression, boost compression, and effective engine compression)
• Finding RPM, gear ratio, speed, transmission ratio, or tire diameter at a given speed with specified gearing and/or tire sizes (uses gear ratio, speed, transmission ratio, tire diameter, and RPM)
• Tire conversion - English to Metric, and Metric to English (uses tire width, aspect ratio, rim diameter, and tire diameter)
• Finding speed with different tire sizes (uses old tire diameter, new tire diameter, speedometer reading, and actual speed)

If you have any suggestions for additional calculators, please contact us.

Estimated Horsepower

Fill in any two of the three values to calculate the third. Weight - The weight of the vehicle in pounds. Trap Speed - The vehicle speed at the end of the 1/4 mile run. Horsepower - Estimated power the engine is making. Weight (lbs) Trap Speed (mph) Horsepower Back to the Top

Estimated Torque

Fill in any two of the three values to calculate the third. Torque - Torque the engine is making. RPM - The RPM the engine is running at. Horsepower - Horsepower the engine is making. Torque (ft-lbs) RPM Horsepower Back to the Top

Estimated ET and Trap Speed

Fill in vehicle weight and horsepower to calculate the ET and Trap Speed. Weight - The weight of the vehicle in pounds. Horsepower - Estimated power the engine is making. ET - The time it takes the vehicle to run 1/4 mile. Trap Speed - The vehicle speed at the end of the 1/4 mile run. Weight (lbs) Horsepower ET (s) Trap Speed (mph) Back to the Top

Adjusted ET Based on Altitude

Fill in any two of the three values to calculate the third. Old ET - The time it took the vehicle to run a 1/4 mile. Elevation - The elevation the 1/4 mile run took place at. New ET - The estimated 1/4 mile time at sea level. Old ET (s) Elevation (ft) New ET (s) Back to the Top

Calculating CFM

Fill in any three of the four values to calculate the fourth. Displacement - The displacement of the engine in cubic inches. RPM - The RPM the engine is running at. Volumetric Efficiency - The efficiency of the engine. A typical engine will run around 80% efficiency, while a tuned engine may run closer to 85%. CFM - Cubic Feet per Minute of air your engine is using (helps to determine desired carburetor size). Displacement (ci) RPM Volumetric Efficiency (%) CFM Back to the Top

Finding Engine Bore and Stroke or Displacement

Fill in any four of the five values (note that the displacement fields are considered one field) to calculate the fifth. Bore - The entire diameter (including overbore) of the pistons. Stroke - The stroke of the engine. # Cylinders - How many cylinders the engine has. Displacement (ci) - The displacement of the engine in cubic inches. Displacement (L) - The displacement of the engine in liters. Bore (inches) Stroke (inches) # Cylinders Displacement (ci) Displacement (L) Back to the Top

Converting Between Liters and Cubic Inches

Fill in any value to calculate the other. Displacement (L) - The displacement of the engine in liters. Displacement (ci) - The displacement of the engine in cubic inches. Displacement (L) Displacement (ci) Back to the Top

Total Effective Engine Compression

Fill in any two of the three values to calculate the third. Motor compression - The compression the engine makes without any power adders. Boost - The amount of boost that the supercharger or turbocharger is producing. Effective compression - The total compression of the engine with the power adder. Motor compression (x:1) Boost (psi) Effective compression (x:1) Back to the Top

Finding RPM, gear ratio, speed, transmission ratio, or tire diameter

Fill in any four of the five values to calculate the fifth. Gear Ratio - The ratio of the axle gear (e.g. 3.55). Speed - The speed of the vehicle. Transmission Ratio - The gear ratio of the transmission gear being used. For example, most overdrives will be around .7 or .8. Use other values depending on the gear. Tire Diameter - The total diameter of the drive tires. This is the height from the bottom of the tread to the top of the tread (if the tire is standing). RPM - The RPM the engine is running at. Gear Ratio (x:1) Speed (mph) Transmission Ratio (x:1) Tire Diameter (inches) RPM Back to the Top

Tire Conversion

Fill in any three of the four values to calculate the fourth. Tire Width - The width of the tire tread. (e.g. on a 255/55/16 tire, the width is 255). Aspect Ratio - The ratio of tire sidewall height to tire tread width. (e.g. on a 255/55/16 tire, the AR is 55). Rim Diameter - The diameter of the rims. (e.g. on a 255/55/16 tire, the rim is 16 inches tall). Tire Diameter - The total diameter of the tires. This is the height from the bottom of the tread to the top of the tread (if the tire is standing). Tire Width (mm) Aspect Ratio Rim Diameter (inches) Tire Diameter (inches) Back to the Top

Finding Speed with Different Tire Sizes

Fill in any three of the four values to calculate the fourth. Old Tire Diameter - The total diameter of original tires. This is the height from the bottom of the tread to the top of the tread (if the tire is standing). New Tire Diameter - The total diameter of the new tires. This is the height from the bottom of the tread to the top of the tread (if the tire is standing). Speedometer Reading - How fast the speedometer (calibrated for the old tires) reads. Actual Speed - How fast the vehicle is actually moving. Old Tire Diameter (inches) New Tire Diameter (inches) Speedometer Reading (mph) Actual Speed (mph) Back to the Top