Gear Ratio Calculators

Input the number of teeth of your ring gear and the number of teeth
of your pinion gear to calculate your rearend gear ratio.

Ring Gear/Pinion Gear Teeth to Gear Ratio
Ring Gear Teeth Count:  / Pinion Gear Teeth Count: Gear Ratio:

Changed your tire size? Guess what - you've also changed your rearend gear ratio.

Find New Gear Ratio With New Tire Size
New Tire Diameter:

Old Tire Diameter: 		Current Gear Ratio: New Gear Ratio:

Get the tire diameter in inches for your metric tires.

Convert P-Metric Tire To Tire Diameter Inches
Example: 195/75R15
/   R 		Tire Diameter:

If you have changed your tire size you've changed the accuracy of your speedometer. 

Speedo Converter
Original Tire Diameter:

New Tire Diameter: 		Speedometer Reading (MPH): Corrected MPH:

Changed your tire size, your rearend ratio etc. and haven't had your
speedometer re-calibrated?  Estimate your true MPH.

Find MPH
RPM:   Tire Diameter:   Axle Ratio:

Transmission Ratio:  *Transfer Case Ratio:
 *Applies to 4-wheel drive vehicles.		MPH:

Find out how accurate your tach is.

Find RPM
MPH:  Axle Ratio:  Transmission Ratio:

*Transfer Case Ratio:   Tire Diameter:
*Applies to 4-wheel drive vehicles.		RPM:
For you 4-wheel drive guys. Your low-low-low gear ratio is, your "Crawl Ratio"? You may
need to do a little research by finding out the transfer case and transmission ratios first.

Find Overall Crawl Ratio
Transmission Ratio:  *Transfer Case Ratio:  Axle Ratio:
*Applies to 4-wheel drive vehicles.		Overall Ratio:
 
Drag Race E.T.

Vehicle Weight (in pounds):  
Vehicle Horsepower:  
RPM through lights (finish line):  
Tire Diameter (Height) in Inches:  
 
1/4 Mile ET:  

1/4 Mile Top End Speed:  

Ideal 1/4 Mile Gear Ratio:  

1/8 Mile ET:  

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