Ratio Calc!

Ratio Calc!

Gearing for your R/C car

25 ratings
64 reviews
$2.99
In-App Purchases

Details

  • Released
  • Updated
  • May 12, 2011
  • November 11, 2025

Features

Ratio Calc! screenshot #1 for iPhone
Ratio Calc! screenshot #2 for iPhone
Ratio Calc! screenshot #3 for iPhone
Ratio Calc! screenshot #4 for iPhone
Ratio Calc! screenshot #5 for iPhone
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About

This app helps radio control car racers calculate their final drive ratio and rollout. Easily select your car, input gear sizes, and get instant results. It also offers charts and saves favorite cars for quick access.

Calculate Final Drive Ratio (FDR)
Calculate Rollout with tire diameter
Filter cars by manufacturer and model
Save favorite cars
Select measurement units (imperial/metric)
Select gear pitch
View ratio and rollout charts
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What's New in Ratio Calc!

7.5.1

November 11, 2025

-Car search now works by manufacturer name as well -Fixed some manufacturer logo display issues -Improved the database update process -Some updated manufacturer logos -Fixed an issue with Zen Racing no longer showing

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In-App Purchases

$0.99

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User reviews

Ratio/tyre sizes

Still unable to adjust tyre sizes and gear ratio. Was excellent before the last update. Shame.

Best roll-out calc out there

Keep it up !!!!!! Your last updated totally made my day.

Response from developer

Thank you! 🙏

Update 7.0 keine Verbesserung!

Liebe Entwickler,
letztes Update ist 5 Jahre her, ich kann den Drang zu aktualisieren verstehen. Jedoch war die RatioCalc App in ihrer vorherigen Version (6.6) sehr gut und übersichtlicher gestaltet als die jetzt gebrachte Version 7.0. Insbesondere die Darstellung als auch Bedienung waren deutlicher abzulesen. Die Übersetzungstabelle z.B. farblich abgesetzt. Einer der meißten genutzten Apps auf meinem Smartphone. Leider kann ich die Version 6.6 nicht mehr laden, schade. Ein perfekter Fall laufende Systeme einfach mal laufen zu lassen. So wie sie jetzt ist fliegt sie aus meinem Smartphone.
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Response from developer

Thanks for the feedback, I believe all of the major issues have now been addressed in the latest update (v7.3).

Update question

was happy to see that you have updated the Ratio Calc app! I’ve been using it for years and am glad to see it’s still being supported. However, I was disappointed to see that you removed the notes feature and the ability to save the same vehicle twice. For example, I often have two 1/12 scale cars—one with a 17.5 rollout and another with a 21.5 rollout.

Will these features be coming back in future updates?
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Response from developer

Thank you. I appreciate the scenario of saving the same car twice isn’t currently possible. The app has had to undergo a full rewrite so some features didn’t make the first cut. I’m currently looking at how best to re-implement the full saving feature currently missing, and hope to have it back soon.

Version 7.0 not fit for purpose

Used this app for years but latest version will not let you change tyre diameters so pretty much useless

Developer apps

FAQ

What does Ratio Calc! do?

Ratio Calc! is a tool designed for radio control car racers. It helps users quickly calculate their car's final drive ratio (FDR) and rollout. This information is useful for comparing gearing with other racers and ensuring the car is set up correctly for track conditions.

How do I use Ratio Calc! to find my car's gearing?

You can select your car by filtering through the extensive database by manufacturer and model. Then, input your pinion and spur gear sizes, and the app will display the FDR. You can also enter your tire diameter to calculate the rollout.

Is Ratio Calc! free to use?

The application is free to download and use, with the option for in-app purchases. This suggests that while core functionality is available for free, some additional features or content might require a purchase.

What kind of cars can I find in the database?

The app boasts a database of over 2000 cars and variants, which is regularly updated. You can filter these by manufacturer and model to find your specific radio control car for accurate gearing calculations.

Can I save my car settings?

Yes, the app allows you to save your favorite cars for quick access. This feature is particularly useful for racers who frequently use the same car or want to quickly compare settings for different configurations.