iPhone Screenshots


Bike Gears is designed for cycling enthusiasts to calculate common gear ratio values: gear ratio, gain ratio, gear inches and development. It's a great tool for bike builders, mechanics, road, mountain, cyclocross or BMX riders and racers.

Use this clean, intuitive, native-app interface to get a quick view of common ratios, or create and share gear charts based on chainring, sprocket, crank length and tire size parameters.

Select a pedaling cadence to calculate bike speed (in both km/h and mph) for a given gear and tire size combination.

Save gear charts for later reference or share them by email.

Gear charts also let you see redundancies in gear combinations and experiment with new combinations to find a set of gearing that works best for your riding style. You can also see bike speed for each gear combination at a set cadence.

Make apples to apples comparisons between bikes using normalized ratios that correct for differences in crank lengths or tire sizes. Use built-in tire size presets or specify a custom tire size for ratio calculations.

Bike Gears supports chainrings with 10-90 teeth and rear sprockets with 8-50 teeth and up to 12 cogs on the cassette. Even if you don't have a 12-cog cassette, use the extra fields to compare cassette options in one chart.

What's New

Version 1.7

Updated for iOS 7 at last!

Version 1.7 includes a number of new features including:
- Select a cadence on the speed chart to see how fast you'll go across your whole gear chart at different cadences. Toggle between km/h and mph.
- It goes to 12! Enter up to 12 cogs on a rear cassette. Even if you don't have a fancy 12-cog cassette, you can use the extra fields to compare different sized cogs on one chart.
- Calculate ratios with a wider range of cadences from 30-180 rpm
- Enter a wider range of gear sizes for both crank and cassette cogs. See your theoretical speeds with an extreme range of values. One can dream...
- Support for 3.5" and 4" screens
- Bug fixes, including correct label for 27 x 2.125 size tire

Ratings and Reviews

Great gear ratio calculator!


Clean, straight-forward interface. All the information is easily viewed in the app and saved for later review. Multiple charts can be created and saved - for comparison between bikes, or to test alternate set-ups for the same bike. The email option allows you to easily share and access the information outside the app in simple, clean tables…a nice bonus. The best bicycle gear ratio calculator I have seen for the iPhone.

Works as advertised


Clean, simple interface. Works well.

120 RPMs is not enough


The app is easy to use and works well except the RPMs stop at 120 so for track or fixed gear calculating a little short.


Bootstrap Apps
663.6 KB
Requires iOS 7.0 or later. Compatible with iPhone, iPad, and iPod touch.
Age Rating
Rated 4+
© 2014 Bootstrap Apps


  • Family Sharing

    With Family Sharing set up, up to six family members can use this app.

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