This calc can be used to find any (one) missing value.
Solve for your MPH.
Solve for your RPM.
Solve for your Differential Ratio.
Solve for your Tire Diameter.
Solve for your Transmission Ratio.
Solve for your Transfer Case Ratio.
Solve for your Crawl Ratio.

If your tires are bigger than stock you probably, like myself, have spend a lot of time trying to WAG (wild ass guess) your actual MPH when going down the road. If you know your gear ratio and tire size you can get a fairly close idea here. Fill in all entries except the one you want an answer to (in green section).

If you'd like to find your overall crawl ratio, enter the Diff/Trans/TransfCase ratios. Remember, the yellow section (crawl ratio) is only for output only, do not type anything in this box.

Clicking on the Transmission or TransferCase links will jump to bottom of this page.

Formulas used


These calculators are color coded by function
All fields Required Leave ONE field blank Supply ONLY one field Results Only