Spur Gear Calculator Hub

Our Spur Gear Calculators are built to help you design and make gears for various applications. We've use high-end commercial software, equations from the American Gear Manufacturing Association (AGMA) governing body, and our own experience to make our calculators as accurate, simple, and accessible as possible.

Whether you're an experienced engineer or first time maker, you can use these calculators to reliably design and inspect all kinds of gears for your project.

Generate a DXF (or SVG) profile of your racks, external, and internal spur gears. Perfect for laser cutting, routing, or importing into your preferred CAD package to integrate into a more complex design that features a spur gear.

Measurement over pins calculator for measuring external and internal spur gears. Use any acceptable pin, specific pin sizes are not required.

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!

Determine how far apart your two gears should be to maintain a proper mesh

Simple input and output, designed for accurate calculations in a suite of free, easy-to-use tools

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

Measure across your gear teeth with calipers for a quick and easy measurement of your gear size and tooth dimensions

Calculate change gears for your gear-making equipment. From hobbers, shapers, generators and lathes, know what gears you need to make the gear you want

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.

Looking to learn more about gears? check out our Gears for Makers training sessions

Convert between module, diametral pitch, and circular pitch for your English and metric gears

Find more calculators, including Viscosity Index and Pitch Line Velocity, as well as additional gearing and related resouces

Make Gears With Us

We've used decades of 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 gear sytem from scratch, reverse engineer a broken gear in one of your machines, or set up small scale manufacturing – we have the experience to make it happen. Reach out with your project and we'll see how we can help.

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Gear design & Engineering

Gear Manufacturing

Gear Inspection

Evolvent Design, LLC

176 N Olive St.

Ventura, CA 93001


(661) 333-3389

AGMA certified | CAGE Code: 8HKE4 | ITAR-Compliant

    We spent the time making these universal calculators to solve common gear problems we have encountered frequently; Design, Process, & Measurement of Internal and External Spur Gears. If you want to design a new transmission, actuator, planetary or other geared mechanism the DXF generator gives you the CAD sketch you need to get started. If you want to process gears in your shop, the Gear Dimension Calculator gives you the key dimensions you need to make your gear blank. Setup your hobber or shaper with our change gear calculator. If you want to reverse engineer a gear that came in through your job shop door, or check your newly processed gear for accurate size, the MOP calculator is for you.
    Engineers will appreciate all the calculators but especially the DXF generator as the sketch can be directly imported into CAD packages as the start of a gear design. Our machinists are now used to looking at the output from the Gear Dimension Calculator to make gear blanks in our manual and CNC lathes.
    The setup will be easier on older equipment using the Change Gear Calculator. Change gear permutations coupled with your machine constants to make any tooth count gear all served up in the most logical order we could determine. Since hobbing machines came late to the CNC party in about 1972 this puts a large quantity of used hobbing machines to benefit from this calculator.
    The Job Shop uses MOP calculator all the time for those jobs that come in off the street. And we like hearing from our customers that it fits "just right". The overlooked Pitch Plate calculator allows you to fixture any gear of any tooth count for further processing after the teeth are cut - yes the technology is in the numbers and the workholding can be done gracefully.
    Internal spur gears are calculated too. Look closely at the DXF and Gear Dimension calculators and open up the world of many new gear combinations, OD to ID, Planetary and more...
But really anyone that is a "Maker" will enjoy using these tools for their projects.

Andrew Prestridge

Evolvent Design, LLC

Closing note from Andrew:  Making gears always took me extra time to calculate and quote, plus the machine setup takes some knowledge as well. With self made and improving calculators the quote, process, and QA/QC steps became quicker. For years they were in spreadsheets and some proprietary code. But they were not easy and definitely not available to everyone in our shop. So I started by transferring them to our internal website, and then onto our public website. With some of the modern web tools they were optimized for mobile too, so everyone can check the numbers anywhere in our company. The "internet" and our work always needed more so I added utility calculators like Gear Center Distance, Span, Pitch Plate and more.
    The world of gears is very interesting to me because of the rich history they have, their interesting complexities, their apparent simplicity, and how a new gear train feels when processed and meshed just right. The manufacturing of metal spur gears can be done in many ways, but the milling, hobbing and shaping processes live in our shop. Your equipment could be any of the following additional processes; wood router, plasma table, 3D printer or a file and with the calculators you have all the data necessary.
    It is amazing to me that our machining forefathers figured it out so long ago. Knowing the history makes me want to improve and do better gear after gear. Use them to make your first gear and everyone after, check out our YouTube and Media posts to see the 5,000 year journey of gears. There are endless ways to combine gears for useful purposes. Many have been discovered, drop me an e-mail with your story and some photos, I would love to see your creative combination.