Here are a few offroad/automotive calculators I’ve gathered during my travels across the web. (Notice I say “gathered” because I’m not nearly smart enough to actually create these on my own.) In each case I’ve put a link to the author. Feel free to give them a shout and tell them how cool these calcs are.

Crawl Ratio Calculator
Crawl ratio is the calculated value of transmission ratio multiplied by transfer case ratio multiplied by axle ratio. The higher the crawl ratio number the more capable your rock crawler should be.

Tire Size to Axle Ratio Calculator
Figure out how to get back the go pedal after installing bigger tires on your rig. This Tire Size to Axle Ratio Calculator will tell you what gears you need to return to stock performance.

Metric to Inches Tire Size Calculator
Translate metric tire sizes into good old fashioned American inches.

Poor Man’s Dyno
Want to know your horsepower, but don’t have access to a dyno? Here’s a quick calculator that’ll tell you estimated HP based on quarter mile time and vehicle weight.

Speedometer Accuracy Calculator
Yes, again bigger tires are causing issues. This time those big mudders are throwing off the accuracy of your speedometer. Find out how fast your really going when the needle’s at 65 MPH.