Speed / RPM Visual Calc

This calculator allows you to interactively change the variables that determine your engine's RPM at any given MPH between 0 and 200. You can alter the axle gear ratio, transmission gear ratio, tire height or profile, and even torque converter efficiency, and see the impact in real-time. For example, you may wish to know what effect that 4.10 ring and pinion will have at highway cruising speed before you buy it. Or, maybe your speedo is inaccurate and you'd like to know how fast you're really going when the tachometer is at 3,000.



Visual Speed and RPM calculator
This calculator allows you to interactively change the variables that determine your engine's RPM at any given MPH between 0 and 200. You can alter the axle gear ratio, transmission gear ratio, tire height or profile, and even torque converter efficiency, and see the impact in real-time. For example, you may wish to know what effect that 4.10 ring and pinion will have at highway cruising speed before you buy it. Or, maybe your speedo is inaccurate and you'd like to know how fast you're really going when the tachometer is at 3,000.

Notes: Consult the numbers below the gauges or the readout in the upper right for the actual RPM and MPH for your selections. The gauges only show approximations. The torque converter efficiency calculation is a bit rudimentary. The revs are adjusted up or down based on the percentage set with the slider control. The transmission gear ratios shown are a Mopar 1968 spec A-833 and 727 Tourqeflite. You can always fill in the custom fields if you know the ratios for your specific vehicle.