Gear Ratio Calculator

At BAKER, our lives are all about multiplying torque. It begins by mastering the math and ends with making sure you stay riding in the best range possible…for the long haul.


This page explains GEAR RATIOS. This is the art and science of optimizing the transmission gear sizes to the desired RPM-vs-Speed performance. The variables we finesse to achieve the perfect balance are the motor sprocket, the transmission gearset, the transmission pulley/sprocket, the wheel pulley/sprocket and the wheel size.

The fundamentals of this mastery reside with the following two equations:

RPM = (S × Sr × Pc × G × 88.00) ÷ (Tc × Sf × Pm)
Speed = (RPM × Tc × Sf × Pm) ÷ (Sr × Pc × G × 88.00)

Use the diagram below to determine what your speed or RPM will be.


S = Speed (miles per hour)

RPM = Engine revolutions per minute

Sr = Rear sprocket tooth count, secondary drive

Pc = Clutch sprocket tooth count, primary drive

G = Gear ratio

Tc = Circumference of rear tire: (diameter (ft.) X 3.1416) (Typical tire is 25” in diameter) Example: 2.083ft. (25”) X 3.1416 = 6.54ft.

Sf = Front pulley/sprocket tooth count (tranny output, secondary drive)

Pm = Motor sprocket tooth count, primary drive


Math is Hard – We’re here to help


At BAKER Drivetrain we notice for some reason a lot of bikers don’t do math. How odd. Now some do it well, but many don’t. So, we’re here to help you through this part.


Feel free to call us TOLL FREE at 1-877-640-2004 and get advice on how to optimize your drivetrain performance.

Fill in the blanks on our RPM vs. Speed Calculator. This popular online tool allows you to finesse, massage, and work the numbers up and down until you reach the desired effect.


To Launch The BAKER RPM Calculator Click On Image Below




BAKER DRIVETRAIN| 9804 E. SAGINAW, HASLETT, MI, 48840 |1-877-640-2004| 517-339-3835 | FAX: 517-339-4590 @2012 BAKER INC