Gear Ratio Calculator

A simple gear ratio calculator to find the speed and mechanical advantage of a gear system of spur gears. Gear ratio is determined solely by the number of teeth on each gear. Check the box if the gear is on the same shaft as the gear above it, leave it unchecked if the gear meshes with the gear above it.


An example gear-train is shown below: The Input Gear meshes with Gear 2. Gear 3 is on the same shaft as Gear 2, and meshes with Gear 4. Gear 5 is on the same shaft as Gear 4, and meshes with Gear 6. The "same shaft" boxes would be checked on Gears 3 and 5 only.

Find, Compare, and Buy the Gear
Cutting Tools You Need to Mill Gears

Using an involute gear cutter to mill a gear

Find the right Spur Gear Calculator from our full list of free tools

When mounting two gears directly next to eachother on separate shafts, use our Gear Center Distance Calculator to find the ideal distance between centers to ensure proper mesh between teeth. If you're looking to create a model of your spur gear, use our free Gear Generator to design external spur gears with ready to download .DXF and .SVG files.

Here's a Quick Summary:

› Input gear parameters

› Use checkboxes to indicate which gears share a shaft

› Calculate output gear ratio