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Gear Calculator — Spur Gear Dimensions

Design spur gears with correct module, tooth count and pitch circle dimensions.

Tooth size factor

How We Calculate This

Spur Gear Formulas

  • Pitch diameter = Module x Number of teeth
  • Outer diameter = Pitch diameter + 2 x Module
  • Root diameter = Pitch diameter - 2.5 x Module
  • Circular pitch = Pi x Module
  • Base circle = Pitch diameter x cos(Pressure angle)

The module determines the size of the teeth. For two gears to mesh, they must share the same module and pressure angle. The pitch circle is where the teeth of meshing gears make contact.

Frequently Asked Questions

Last updated: February 2026

All calculations are estimates. Always verify settings with test prints before committing to final prints.