Gear Rack Calculator

The gear rack calculator calculates the key dimensions for a gear rack. Based on the module (or diametral pitch) you can easily get the gear tooth dimensions, including addendum, dedendum, whole depth, tooth pitch, root fillet radius, and more. Measurement over Pins (or balls) for a rack gear is a great inspection method and this calculator gives a range of acceptable ball sizes. Once you select a ball size, add the distance from the pitch line to the back of the rack (datum) to calculate the appropriate Measurement over Pin value.

The general form of the rack is the same for Forms A-D, with Form C being the most common. The only difference between the Forms (as specified by ISO 53) are the clearance depth and root fillet; DIN 867 allows for a continuous range of clearances and root fillets, within the same bounds as ISO 53.

Be sure to check out our diametral pitch calculator if you need to convert from circular pitch


Results conform to ISO 53:1998 Standard basic rack tooth profile for rack profile and ANSI/AGMA 2002-D19 Tooth Thickness and Backlash Measurement of Cylindrical Involute Gearing for measurements over pins. DIN 867 Basic rack tooh profiles concurs with ISO 53 allows for a broader range of clearance and root fillets.

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What is a Gear Rack?

A Gear Rack is essentially a spur gear with an infinite number of teeth. As the number of teeth on a gear increases it starts to look flatter and flatter; a gear rack is the extension of that: a gear that has been stretch to a straight line. While spur gears are circular and have a curvature, a gear rack has teeth along a straight line that would mate with a spur gear.

ISO Rack Forms (A-D)

ISO 53 is a guiding document for standard rack gear forms. The differences between Form A and Form D are relatively minor, and relate mostly to the clearance and root fillet radius beneath the working depth of the rack. In general, Form A is recommended for transmitting high torques while Forms B and C are for general purpose, or normal service, applications. Form D has a full radius form for the root fillet and is recommended for high-precision gears transmitting high torques

Here's a Quick Summary:

Gear rack dimensions are based on module

Measurement over pins works from a datum

Units (inch or mm) need to be consistent