Gear Ratio Calculator

A gear ratio compares how many turns the driving gear makes per turn of the driven gear. An axle ratio of 3.73 means the driveshaft spins 3.73 times for each turn of the wheels.

Divide the ring gear tooth count by the pinion tooth count. For example, 41 ring teeth over 11 pinion teeth gives 3.73, a common truck and towing gear set.

Yes. A higher ratio such as 4.10 multiplies torque for quicker acceleration off the line, but it raises engine rpm at any given speed, which usually lowers fuel economy and cruising comfort.

Wheel rpm equals engine rpm divided by the ratio. Multiply wheel rpm by the tire circumference in inches, then by 60 minutes, and divide by 63360 inches per mile to get mph.

No. It treats the engine speed as going straight through the final drive, which matches a 1:1 top gear. If your gear is not 1:1, multiply the ratio you enter by that transmission gear ratio first.

This is an ideal figure with no tire slip, no wear and no speedometer error. Worn or underinflated tires shrink the rolling diameter, and factory speedometers often read a few percent high, so small gaps are normal.

Yes. Any gear ratio is the driven tooth count divided by the driving tooth count, the same math as ring over pinion. Put the driven count in the ring box and the driving count in the pinion box.

Use the overall loaded diameter of the mounted tire in inches, not the rim size. You can read it from a tire spec sheet or work it out from the tire size with a tire size calculator.

Yes. Every figure is computed in your browser with no upload, so your build details stay on your device and the calculator keeps working with no connection.