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Ratio Calc!

Ratio Calc!

R/C car gearing

25 ratings
80 reviews
🔧 Utilities
⚽ Sports
$2.99 Free
In-App Purchases

Lowest price: Free a year ago (-100%)

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Price history

Details

Released
May 12, 2011
Updated
October 8, 2026

Features

Developer

David Mills
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🔄6+ apps
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❓5 answered
FAQ↘︎
📦~ in 3 months
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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
Show original description

What users say about Ratio Calc!

Reviews of Ratio Calc! are mixed: the Sports app is rated 4.5/5 from 25 App Store ratings. What users like most: excellent for RC gear ratios, great database of cars. Top complaints: latest version unusable, cannot adjust tyre sizes. Summarized from real user reviews.

Positive things

  • 👍Excellent for RC gear ratios
  • 👍Great database of cars
  • 👍Simple and easy to use
  • 👍Invaluable at the track
  • 👍Time saver
  • 👍Good for calculating FDR
  • 👍Functional without distractions
  • 👍Well-designed interface
  • 👍Adds new cars quickly
  • 👍Useful for setup and tuning
  • 👍Comprehensive vehicle database
  • 👍Great for beginners and pros
  • 👍Saves money on motors/controls
  • 👍Good for dirt oval applications
  • 👍Top tool for RC car owners
  • 👍Excellent app
  • 👍Very helpful
  • 👍Works great

Negative things

  • 🐛Latest version unusable
  • 🐛Cannot adjust tyre sizes
  • 🐛Cannot adjust gear ratio
  • 🐛Removed notes feature
  • 🐛Removed ability to save same vehicle twice
  • 🐛Older versions were better
  • 🐛Less clear than previous version
  • 🐛Update not an improvement
  • 🐛App needs updating
  • 🐛Lacks Mod 1 pinions/spurs
  • 🐛Does not support 1:8 e-buggies
  • 🐛Bug on iPad: 'done' button missing
  • 🐛Cannot select gear pitch per car
  • 🐛Lacks input for battery/motor specs
  • 🐛Lacks speed chart for comparison
  • 🐛Needs more car models
  • 🐛Needs to update new kits
See all reviews

What's New in Ratio Calc!

7.6

October 8, 2026

-Updated for the latest devices -Refreshed database -Fixed a few small bugs

More
4

Subscriptions & In-App Purchases

$0.99

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Nice Tip Amount

User reviews

Most RecentHighest RatedLowest Rated

Ratio/tyre sizes

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

Best roll-out calc out there

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

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.
Show more
RRhinegower

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?
Show more
WWrxmoose

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
J6Jon 682
See 75 more reviews

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User experience

🐞

Reported Bugs

5 issues

Cannot adjust tyre sizes in latest version

Bug

Cannot adjust gear ratio in latest version

Bug

Bug on iPad: 'done' button missing after setting pinion/spur

Bug

Removed notes feature in latest update

Bug

Removed ability to save same vehicle twice in latest update

Bug
✨

Requested Features

13 requests

Add Mod 1 pinions and spurs

Feature

Add support for 1:8 e-buggies

Feature

Reintroduce notes feature

Feature

Reintroduce ability to save same vehicle twice

Feature

Add iCloud backup or import/export feature

Feature

Add option to attach setup sheets/track data

Feature

Add input for battery used and motor specs

Feature

Add speed chart for comparison

Feature

Allow selection of gear pitch for each car

Feature

Update app to include new kits

Feature

Add more car models

Feature

Divide Asphalt into 1:12 and 1:10 categories

Feature

Add watch app

Feature

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.