# Ratio Calc! — Gearing for your R/C car

> Radio control car gearing calculator for final drive ratio and rollout. (iPhone/iPad app by David Mills.)

- Source: https://appshunter.io/ios/app/ratio-calc/id436311293 (this page in markdown: same URL + `.md`)
- Developer: [David Mills](https://appshunter.io/developer/395985551)
- Category: Sports, Utilities
- Price: $2.99 with in-app purchases
- Rating: 4.50/5 from 25 App Store ratings · 64 written reviews indexed
- Age rating: 4+
- Requires: iOS 16.6 · 46 MB
- Languages: American English, German (Germany), Italian, European Spanish
- Released: 2011-05-12
- Data updated: 2026-09-10
- Monetization: free with in-app purchases
- User reviews in markdown: https://appshunter.io/ios/app/ratio-calc/id436311293/reviews.md

## What is Ratio Calc!?

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.

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

- Select measurement units (imperial/metric)

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

- Over 2000 cars/variants in the database which is updated regularly

## Key features

- 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

## Pricing and in-app purchases

Base price: $2.99.

**One-time purchases**

| Purchase | Price | Type |
| --- | --- | --- |
| Nice Tip | $0.99 | one-time |
| Generous Tip | $2.99 | one-time |
| Mega Tip | $4.99 | one-time |
| Insane Tip | $9.99 | one-time |


## Recent user reviews (10 of 64)

All indexed reviews: https://appshunter.io/ios/app/ratio-calc/id436311293/reviews.md

### 1/5 — Ratio/tyre sizes

*2026-02-22*

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

**Developer response:** Help me out please, and get in contact so I can try to understand the problem: https://sllim-code.com/contact-us/ Tyre size is definitely adjustable so I’m a little confused. Thanks!

### 5/5 — Best roll-out calc out there

*2024-12-08*

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

**Developer response:** Thank you!  🙏

### 1/5 — Update 7.0 keine Verbesserung!

*2024-11-27*

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.

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

### 2/5 — Version 7.0 not fit for purpose

*2024-11-26*

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

**Developer response:** I’ve improved tyre diameter entry now and I believe all of the major issues have now been addressed in the latest update (v7.3).

### 4/5 — Update question

*2024-11-26*

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?

**Developer response:** 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.

### 5/5 — Please create this for android

*2024-02-21, version 6.6*

I have the app for iphone but I've recently switched to android and would love to use this on my new phone for my rc racing.

### 4/5 — Modelle

*2023-08-11*

Hallo, bitte bei Xray den TW X4 einpflegen

### 5/5 — Great App - needs an update though

*2022-10-19*

Not a major issue as plenty of cars have not actually changed their internal ratio, but many will look and wonder where there car is….!

### 4/5 — Nicht ganz Aktuell

*2022-03-30*

Während der neueste Tamiya TA08 aufgeführt ist, fehlt das aktuelle Flaggschiff TRF420…
Ansonsten eine gute Idee

### 5/5 — Génial

*2021-05-29*

Un outil top pour tous les possesseurs de voiture RC!

## Frequently asked questions about Ratio Calc!

### 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.

## Version history (last 5 releases)

### 7.5.1 — 2025-11-11

-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

### 7.5 — 2025-09-22

-Improved search results now show the correct number of results
-Updated for iOS 26
-Latest version of the car database

### 7.4.1 — 2025-01-08

-Improved the app layout when landscape on the largest phones

### 7.4 — 2024-12-11

-Fixed an issue with the charts disappearing for saved cars - thanks Ali!
-Pull to refresh on the Manufacturers list now updates the car database

### 7.3 — 2024-12-07

-You can now save cars, with notes etc
-Saved cars can now be amended

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## More apps by David Mills

- [Race Dash Legacy](https://appshunter.io/ios/app/race-dash-legacy/id1071528179)
- [Race Dash for Sim Games](https://appshunter.io/ios/app/race-dash-for-sim-games/id1174914156)
- [Brexipocalypse](https://appshunter.io/ios/app/brexipocalypse/id1481865013)
- [Mortgage Calc: fast and simple](https://appshunter.io/ios/app/mortgage-calc-fast-and-simple/id6751363275)

All apps by David Mills: https://appshunter.io/developer/395985551

## Related topics

[rc rollout calculator](https://appshunter.io/ios/topics/rc-rollout-calculator)

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*Data collected daily from the US App Store and indexed by [AppsHunter](https://appshunter.io/). User reviews are verbatim App Store reviews. Ratings, prices and chart positions refresh continuously; this snapshot is from 2026-09-10.*