Gear Ratio & Speed Calculator
Calculate vehicle speed at a given RPM from transmission gear ratio, axle (diff) ratio and tyre diameter — or RPM at a given speed.
Enter your values and press Calculate.
How to use the Gear Ratio & Speed calculator
Calculate vehicle speed at a given RPM from transmission gear ratio, axle (diff) ratio and tyre diameter — or RPM at a given speed. Enter your values above and press Calculate; the result appears instantly, and the formula used is shown below so you can check the working.
Formula
MPH = RPM × tyre diameter ÷ (gear ratio × axle ratio × 336)
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