Gear Dimension Calculator

Gear Pitch Calculator: Find Pitch Diameter, Gear Blank Outer Diameter (OD), and Root Diameter

Calculate the key dimensions for your external spur gear. Input the gear's tooth count, pitch (or module), and pressure angle to calculate the pitch diameter, root diameter, and outer diameter. This also generates the tooth dimensions: addendum, dedendum, working depth, and whole depth.


The default Manufacturing Profile Shift Coefficient is 0. Positive values result in thicker teeth, as if your cutting tool did not cut to a full depth, while negative values result in thinner teeth. Looking to 3D print, router, or laser cut a spur gear? Use our free Gear Generator to create internal or external spur gears and rack and pinion sets - all with ready-to-download .DXF or .SVG files.

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Gear Blank Calculator

We built this spur gear calculator to ensure we had the right measurements for making gear blanks in our shop. Having the right gear blank is an essential part of the gear-mkaing process, and helps ensure your gear is within tolerance

Gear OD Calculator

Calculating the outer diameter, or OD, of your gear is important to ensure that you make the gear correctly and that it will mesh properly with its mate. Many gear-making processes (including hobbing, milling, and shaping) rely on the operator accurately touching-off on the part.

During the touch-off the operator slowly brings the cutting tool into the gear blank until it just begins to touch, then the full depth is dialed in relative to the touch-off. If the gear blank is the wrong size, the touch-off will occur at the wrong position and the cut will either be too shallow or too deep

Gear Pitch Diameter Calculator

Calculating gear pitch diameter can be done by dividing the number of teeth on the gear by its diametral pitch. For imperial gears, the Diametral Pitch will generally be an integer ranging from 3 (for very large gears) to 64 (for very small gears).

How to Calculate Pitch Diameter of a Gear?

In short, divide the number of teeth on the gear by the diametral pitch of the gear to calculate its pitch diameter. The units of diametral pitch are 1/inches, so the units of the pitch diameter will be in inches.

For a quick approximation, the pitch diameter is roughly in the center of the gear tooth. Gears have approximately the same length from the pitch diameter to outer diameter (addendum) as from the pitch diameter to root diameter (dedendum).

Gear Module Calculator

Calculating gear module can be down by dividing the gear pitch diameter by the number of teeth on the gear. A gear's module is very nearly the inverse of the its diametral pitch, however module is expressed in millimeters while diametral pitch is 1/inches.

How to Calculate Module of a Gear?

Divide the pitch diameter (in millimeters!) of a gear by its number of teeth to get the module of a gear. Alternatively, 25.4 divided by the diametral pitch of the gear will also give you its module.

How to Check Gear Dimensions?

After cutting your gear teeth, measuring and inspecting your gears is essential to ensuring your gears are perfectly in-spec for their application. Using a Measurement Over Pins Calculator can make sure your gear is the right size using pins or wires.

gear dimension calculator

Gear Dimension Calculator

› Input gear parameters

› Output gear dimensions

› Ready to make a gear blank!