Figure out what Spur, Pinion, or Size of Tire You Need to Run

Solve for Rollout       Solve for Pinion
Tire Diameter

Transmission Ratio

Spur Gear


Total Rollout





Another Calculator to Find Rollout

GearWizard Calculator: Tire/Gearing Ratio Calculator

GearWizard Rollout Calculator
This calculator will allow you to determine the correct rollout ratio based on just a few inputs.
Data InputResults
If you do not understand any particular term, just slide your mouse over it for a definition
Outer Tire Diameter
Spur Gear
Pinion Gear
Transmission Ratio : 1

"Click in the Blue or Brown  area after putting input to change your Results"

A higher rollout number results in slower acceleration and greater top speed. Lower rollout results in the opposite.
Tire Circumference
Pinion:Spur Ratio
Gearing Quotient
Rollout Ratio
Although this calculator works for most motors, some require different gearing to compensate for heat issues. Always check your motor every few minutes to see if it is getting too hot. With a properly geared motor, you should be able to hold your finger directly in the center of the can for at least 5 seconds. Anything less than that, and you are overgeared.

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