4x4OffRoads.com - 4x4 Off Road Calculator Use this program for calculations for your modifications project. It currently has three mini-calculators. Select your calculator by clicking on the various tabs. Tire Size Calculator Converting from metric tire size to the more common inches used in those larger 4-wheeling tires can be handy. New Gear Ratio Calculator When you get larger tires you have to lower the gear ratio to preserve fuel consumption. This 4x4 Calculator can help you to find the ration closest to the original setup. Crawl Ratio Calculator High overall crawl ratio means you can go slower - that transforms into better off road capabilities.