• BMX Gear Calculator iPhone/iPad app


bmxultra.com Gear Chart Calculator – Accuracy

There is no denying that the free bmxultra.com online gear calculator or even the iPhone/iPad app are very handy tools for the modern day BMXer looking to squeeze to most performance out of their racing. Originally built for ourselves over a decade ago, it’s transformed to the most used gear calculator used in BMX racing today.

The calculator allows you to select the number of teeth you run on the front and rear sprockets on your bike, as well as the tire brand, model and size. It calculates the gear inches based on your selections.


The calculation is quite simple

gear inches = drive wheel diameter in inches X number of teeth on front chain ring / number of teeth on rear sprocket

We created the calculator as a quick guide or handy reference, so you don’t need to worry about it.

We add new tires and sizes to the free online calculator first because it’s something we can do in-house. We store up changes for the App because we have to pay a developer to update that and we want to keep the calculator affordable.

From time to time we are questioned about the accuracy of the calculations. As accurate as we like to keep the calculator it’s not as perfect as taking your own tire measurements, but it is a whole lot quicker and easier.

There are many factors that will alter the outer diameter of the tire

  • The tire pressure is a major contributing factor, over on under inflating your tire can change the shape of your tire
  • The width of your rims can vary and also change the shape of the tire
  • Wear can also be a factor

I’m sure you can imagine it would be quite difficult to create a calculator that would take all of these into consideration.

Our calculations are based on the maximum recommended tire pressure, which makes them a great guide to the differences between gear combinations.

The calculator also allows you to store a number of set ups so you can keep track gearing set ups for your entire family.

If you haven’t seen or used the calculator before try these links for the free online gear calculator or the iPhone/iPad app.

We always love to hear feedback about our calculator, and have made a number of changes over the years based on user feedback. If you have an idea that would help make the calculator more useful be sure to email webmaster@bmxultra.com.

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