Use our Differential Gear Ratio Calculator page to determine the best ring and pinion gear ratio for your vehicle. Installation of the correct ring and pinion gear ratio will help optimize performance, fuel economy and overall driveability.

Tire Diameter Calculator

In order to select the ideal differential gear ratio, the first thing you will need to know is your actual tire diameter. The simplest method is to measure the height of the tire from the ground to the top of the tire.

If you don’t actually have the tires installed on the vehicle yet, use the metric tire diameter calculator below to determine tire diameter (height) using metric size designations.

Metric tire specifications use a three number format, such as 275/75R16, where 275 is the WIDTH of the tire tread in millimeters, 75 is the ASPECT (or percentage of tread width to yield the sidewall height), and 16 is the WHEEL diameter. Using the calculator below and the numbers in this example, the calculated value will be 32.24″.

The calculated value should be used only as a guideline for RPM calculations. Tires with identical specifications that are made by different manufacturers may have different actual diameters.

Truck and off road tires may have a specification like 30×9.5R15, where 30 is the tire diameter, 9.50 is the tread width and 15 is the wheel diameter. You don’t need the tire diameter calculator in this case, but be advised that most stated tire sizes rarely match the actual tire height. In the example above, 30 might not be completely accurate.

Need help? Our gear and axle experts will be happy to assist at (800) 510-0950

 

Tire Diameter Calculator




The Tire Diameter:

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RPM Calculator

Use the RPM calculator to determine what RPM your engine will run based on gear ratio, tire diameter, transmission and MPH. You can try various combinations to come up with an appropriate combination of ring and pinion gear ratio and tire diameter for your vehicle. The RPM calculator should be used as a guideline for comparative purposes only. Your vehicle will probably run at different RPM’s than those you calculate. See What gear ratio do I need in FAQ for a discussion on choosing a ratio. Find all of the gear ratios available for your vehicle in our Application Guides

Need help? Our gear and axle experts will be happy to assist at (800) 510-0950

RPM Calculator




Your RPM is about

Automatic without Overdrive:

Automatic with Overdrive:

Manual:

5 Speed:

Recommended Engine RPM @ Highway Speed
  • 4 cylinder: 2200 – 3200
  • V6 cylinder: 2000 – 3200
  • Small block: 1800 – 2800
  • Big block: 1800 – 2600
  • Diesel: 1600-2800

Find all of the gear ratios available for your vehicle in our Application Guides or call our staff of differential experts at (800) 510-0950 for LIVE help.

West Coast Differentials stocks a huge inventory of OEM and Aftermarket Ring & Pinion Gear sets and orders placed before 4 PM Pacific Standard time usually ship the SAME DAY! We have the Differential Gears to match your budget and performance needs.

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Differential Gear Ratio Calculator

Enter the number of teeth on your ring and pinion gear set to find the gear ratio. Example: Ring Gear / Pinion Gear = Ratio

Gear Ratio Calculator



Your gear ratio is

Find all of the gear ratios available for your vehicle in our Application Guides or call our staff of differential experts at (800) 510-0950 for LIVE help.




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Order by Phone

Need your parts ASAP?

For the fastest service, call our Differential Parts Experts at (800) 510-0950 for immediate assistance. We are available to help Monday thru Friday from 8 AM to 5 PM Pacific Standard Time, and most orders placed by 4 PM ship out the SAME DAY!

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