Ratio Calc‪!‬ 4+

Gearing for your R/C car

David Mills

Designed for iPad

    • $2.99
    • Offers In-App Purchases


Ratio Calc is a quick and easy tool for radio control car racers to use trackside. Knowing your final drive ratio (FDR) is very useful for comparison with other racers to determine if your car is geared correctly. You can also view your favourite information on Apple Watch.

It lets you quickly select your car by filtering on manufacturer and model. Select your pinion and spur size and the FDR is displayed. Tyre diameter can also be entered to calculate your rollout.

Ratio and roll out charts are also available which plot pinion and spur gear combinations to create very handy reference tables.

- Save your favourite cars for quick access

- Save notes and track name against your favourite cars

- Share ratio/rollout charts

- Download new cars from within the app

- Select measurement units (imperial/metric)

- Select your preferred gear pitch, alternative ratios in other pitches will be shown

- Over 1600 cars/variants in the database

What’s New

Version 6.6

-Support for the latest devices and iOS
-Improved the database update process to show more details
-Removed the text erasing buttons on the text fields when editing notes
-Moved the gear and diameter pickers up so that the results can be seen whilst changing the settings
-Updated database and manufacturers
-Various other little tweaks and improvements

Enjoy your R/C racing!

Ratings and Reviews

4.6 out of 5
18 Ratings

18 Ratings

Korelick ,


Well done! I love the amount of cars you have in the library. Great tool!

Speed2Burm ,


Great place to keep notes and gearing for all your cars. Enough models for every occasion!!! Store multiple cars and compare final drive ratios or roll out for accurate records. Will definitely save money on spent motors and speed controls due to over gearing.

nazzy5x ,

Ratio Calc

App needs to be updated!

Developer Response ,

Can you elaborate please? The database of cars is updated regularly - if there’s one missing then drop us an email and we’ll do our best to add it.

App Privacy

The developer, David Mills, indicated that the app’s privacy practices may include handling of data as described below. For more information, see the developer’s privacy policy.

Data Not Collected

The developer does not collect any data from this app.

Privacy practices may vary, for example, based on the features you use or your age. Learn More

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