Clear outputs, easy Excel integration, and reliable results for every project.
Our Spur Gear Calculators are designed to help you both design and manufacture gears. They are based on gear manufacturing standards, established industry practices, and our own experience. The outputs are clear and can be easily copied into Excel for further use.
Whether you are a design engineer, a machinist, or a job shop quoting its first gear, these calculators provide reliable support. You can use them for both the design and inspection of gears in your projects.
Tools
Our Calculators
Generators
Spur Gear Generator
Generate a DXF (or SVG) profile of your racks, external, and internal spur gears. Perfect for laser cutting, routing, water jet cutting, or importing into your preferred CAD package to integrate into a more complex design that features a spur gear.
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3D .STL Gear Generator
Generate 3D .STL models of involute spur gears, perfect for 3D-printing, or importing into your preferred CAD or modeling package.
Open calculatorGear Geometry
Gear Dimension Calculator
Get all of the dimensions you need to make your gear blank: tip, pitch, root diameters; as well as the gear teeth: addendum, dedendum, working depth, whole depth. External and Internal Spur Gears!
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Center Distance Calculator
Determine how far apart your two gears should be to maintain a proper mesh
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Gear Ratio Calculator
Determine your input and output speed for a gear train of up to eight gears. This calculator has a provision for gears on the same shaft, so you can enter them as you see them
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Gear Rack Calculator
Determine the fundamental gear rack geometry (addendum, dedendum, depth, pitch, etc.), as well as Measurement over Pins for a gear rack
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Pitch Converter
Convert between module, diametral pitch, and circular pitch for your English and metric gears.
Open calculatorDid you know? Having a prime tooth count gear in your transmission spreads wear evenly for longer life.
Measurement & Inspection
Measurement Over Pins (or Wires)
Measurement over pins calculator for measuring external and internal SPUR and HELICAL gears. Use any acceptable pin, specific pin sizes are not required. Often the measurement is called Measurement over Wires (MOW).
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Worm Measurement Over Pins
Also called "Measurement over Spheres," this calculator will help you measure worm shafts (paired with wormgears) for pitch diameter and backlash
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Gear Span Calculator
Measure across your gear teeth with calipers for a quick and easy measurement of your gear size and tooth dimensions.
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Vari-Roll Distance Calculator
Calculate the test spacing for your Vari-Roll or other gear checkers. Uses the shaft diameter then: center distance, gear geometry, or test diameter to output spacing and gauge blocks.
Open calculatorDid you know? You can inspect gears with simple gage pins and ball bearings.
Gear Strength
Gear Strength Calculator
Determine the maximum horsepower your gear pair can transmit, based on material, geometry, application, and more
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Lewis Form Factor
Determine the maximum load a gear can withstand via the Lewis Form Factor method
Open calculatorDid you know? The pinion tooth count has a lower limit for strength due to undercut.
Machine Setup & Shop
Change Gear Calculator
Calculate change gears for machine tools. From hobbers, shapers, generators and lathes, know what gears you need to make the gear you want.
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Pitch Plate Calculator
Use three pins to make your own gear work-holding solution, or to make a set of GO/NO-GO gauges to help qualify the gears you make or receive. Want to align a gear tooth to another feature on the hub, this calculator will do the geometry for you.
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Dividing Head Calculator
Calculate the turns and holes for common dividing head ratios: 40:1, 60:1, 90:1.
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Lead Angle - Worms & Hobs
Calculate the lead angle for worms and gear hobs, works with Diametral Pitch and Module.
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Lead Angle - Threads
Calculate the lead angle for threads on screws and bolts, works with TPI, Pitch, and Lead.
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"I just wanted to say THANK YOU, THANK YOU, THANK YOU ...
Better tool than Machinery's Handbook on spur gear calc's."
Make Gears With Us
We've used our gear design and manufacturing experience to make these universal calculators, solving common gear problems we've encountered in our own shop over the years.
We've worked on both projects big and small, and at every stage of the process. Whether you're looking to design a new transmission from scratch, reverse engineer a broken gear, set up small scale manufacturing, or refurbish and upgrade a machine. Reach out with your project and we'll see how we can help.
Gear Manufacturing
Gear design & Engineering
Gear Inspection
Evolvent Design, LLC
176 N Olive St.
Ventura, CA 93001
contact@evolventdesign.com
(661) 333-3389
ISO 9001:2015
Why We Built These Calculators
We built these universal tools to solve the most common gear problems we face: design, geometry and sizing, processing, and inspection of internal and external spur gears.What You Can Do
Design new mechanisms: Use the DXF Generator to create CAD sketches for transmissions, actuators, planetary systems, and more. (outputs SVG formats too)
Process gears in your shop: The Gear Dimension Calculator provides the key blank dimensions.
Set up your machines: The Change Gear Calculator makes it easier to configure hobbers and shapers, even on older machines.
Inspect or reverse-engineer: The MOP Calculator helps verify gears or measure unknowns.
Fixture gears for secondary ops: The Pitch Plate Calculator handles any tooth count.
Who Uses Them
Engineers love the DXF Generator because its sketches import directly into CAD.
Machinists rely on the Gear Dimension Calculator for making blanks on manual and CNC lathes.
Job shops use the MOP Calculator for quick inspections and customer jobs.
Robotics and actuator designers prototype planetary and low-tooth-count drives with the generators.
Bonus - INTERNAL GEARS
These tools also support internal spur gears and open up new possibilities: OD-to-ID, planetary, and beyond.
GearCalculators.com is powered by Evolvent Design, offering advanced tools for gear engineers and shops.
Andrew Prestridge
Evolvent Design, LLC
Gears have a 5,000-year history, yet every new combination still feels fresh and full of possibility. Use these calculators to create your first gear and every one after — and check out our YouTube and media posts to follow the journey.
– Andrew Prestridge