# Watch Gear Calculator — Watchmakers' Gear Calculator

> Watch gear train diagnostic calculator for watchmakers. (iPhone/iPad app by David Margolis.)

- Source: https://appshunter.io/ios/app/watch-gear-calculator/id6736832989 (this page in markdown: same URL + `.md`)
- Developer: [David Margolis](https://appshunter.io/developer/1773372938)
- Category: Utilities, Productivity
- Price: Free with in-app purchases (on sale, was $9.99)
- Age rating: 4+
- Requires: iOS 17.5 · 5 MB
- Languages: American English, French (France)
- Released: 2024-10-22
- Data updated: 2026-08-22
- Monetization: free
- User reviews in markdown: https://appshunter.io/ios/app/watch-gear-calculator/id6736832989/reviews.md

## What is Watch Gear Calculator?

Watch Gear Calculator helps watchmakers diagnose issues in watch gear trains. It is ideally used in conjunction with a TimeGrapher with a trace function.
 
If a trace shows a significant change in amplitude at a regular frequency, Watch Gear Calculator will help you identify the likely cause. You input the number of teeth / leaves for each wheel and press calculate. You are presented with hh:mm:ss results for turn time, tooth passage and more for each wheel. Whichever result matches the frequency of issues seen on the trace will reveal where the problem is.
 
For example, perhaps your trace shows a reduction in amplitude every five minutes. This matches a 00:05:00 result for Barrel Mesh Time. Meaning the issue is caused by the meshing of the Barrel teeth with the Second Wheel pinion. It likely means the barrel is tilting and you need to re-bush the barrel bridge.

How to Use
When the app opens or you reset it, you setup the calculation by providing basic information about the movement's BPH and RPMs of 2nd and 4th wheels if known. You must be able to answer at least 1 of 3 questions . If in doubt, providing just the movement's BPH is fine. Or, if you're not sure about the BPH but you know the 4th wheel rotates once per minute, that's fine too. The BPH will be calculated. More information will mean fewer teeth to count and help the calculator validate results.

Next you fill in all the white fields with tooth counts. Simply hit calculate when you have inputed everything. Missing or invalid fields will turn red.

Once you have calculated, you can make changes to any of your inputs. Doing so will clear off invalid calculations and you will have to hit calculate again to refresh the results.
 
To save, enter the name of the movement and hit save. Hit My Calcs to see all your calculations and calculations that have been shared by other users. If you want to share your calculations with everyone, just hit share and follow the prompts.

How To Interpret Calculations
​
You will mostly be relying on Turn Time, Tooth Passage and Hunting Tooth Frequency to diagnose issues. These are all displayed in hours, minutes, seconds and milliseconds. Gear Ratio and RPM are also provided for completeness.
 
Turn Time - The time it takes for a wheel to complete a full turn. An abrupt drop in amplitude matching this frequency indicates a damaged tooth or pinion leaf. A gradual wave matching this frequency indicates a bent pivot or an out-of-true wheel.
 
Mesh Time - Also known as Tooth Passage. The time it takes for a given tooth to engage and disengage with a pinion leaf. If this shows on the trace, the problem is likely to be caused by incorrectly meshing teeth. This is very common between the Great Wheel and the Second Wheel and often indicates worn bushes causing the barrel to not be fully upright.
 
FHT - This is the "Hunting Tooth Frequency" of the wheel and its meshing pinion. This is an unusual calculation not well known in horology. It is commonly used in gear vibration analysis for cars. But it is extremely useful in watchmaking too. If both a tooth and a pinion leaf were damaged, this is the frequency at which they will make contact. This might be seen on a trace as a seemingly random drop in amplitude every so often. Or even a watch that stops for no obvious reason. If the time between stopping matches a hunting tooth frequency, then you have identified the cause.
​
HCF - This subject requires more explanation and we are limited by word-count on the App Store! Please visit the info page via the app to learn more about HCF.

## Key features

- Diagnose watch gear train issues
- Input tooth counts and movement BPH
- Calculate turn time, tooth passage, and FHT
- Interpret trace irregularities
- Save and share calculations
- View shared user calculations

## Pricing and in-app purchases

Base price: Free.

**One-time purchases**

| Purchase | Price | Type |
| --- | --- | --- |
| Unlock Pro | $9.99 | one-time |


## Recent user reviews (2 of 2)

All indexed reviews: https://appshunter.io/ios/app/watch-gear-calculator/id6736832989/reviews.md

### 5/5 — Great App

*2025-02-07, version 1.3.2*

A great app ! Would be good to see period of oscillation it would also be great for students to see the formulas used.

### 5/5 — A great time saving tool for watchmakers

*2024-10-23, version 1.02*

Does exactly what it proclaims to do. A highly useful and easy to use tool.

## Frequently asked questions about Watch Gear Calculator

### What is Watch Gear Calculator used for?

Watch Gear Calculator helps watchmakers diagnose problems in watch gear trains. It analyzes irregularities shown on a TimeGrapher trace by calculating metrics like turn time and tooth passage based on user-inputted gear data.

### How do I use Watch Gear Calculator?

You start by inputting the movement's BPH or wheel rotation speeds. Then, you enter the tooth counts for each wheel. Pressing 'calculate' provides results to help identify the source of amplitude changes seen on a trace.

### Can Watch Gear Calculator be used offline?

The provided data does not specify offline functionality. However, the app's core function involves calculations based on user input, suggesting it may operate without a constant internet connection for basic calculations.

### What information is needed to use Watch Gear Calculator?

You need to provide the number of teeth for each wheel in the gear train. Optionally, you can also input the movement's BPH (beats per hour) or the RPMs of the 2nd and 4th wheels for more accurate calculations.

### Does Watch Gear Calculator have ads?

No, Watch Gear Calculator does not contain advertisements. The app is free to use and does not display any ads to users.

### How often is Watch Gear Calculator updated?

The latest version is 1.4.0, released on January 6, 2026. While specific update frequency isn't detailed, this indicates recent development and ongoing support for the application.

### What devices is Watch Gear Calculator available on?

Watch Gear Calculator is available for both iPhone and iPad devices. It is designed to run on Apple's mobile operating systems.

### Can I save and share my calculations with Watch Gear Calculator?

Yes, you can save your calculations by naming the movement and hitting save. You can also share your calculations with other users and view calculations shared by the community.

## Version history (last 4 releases)

### 1.4.1 — 2026-04-15

Added French and Swiss French localisations. Various bug fixes.

### 1.4.0 — 2026-01-06

Bug fixes and restored shared calculations. Watch Gear Calculator is now free to download. You can pay to unlock "Pro" version for advanced calculations. Anybody that previously downloaded the paid version should automatically be upgraded to Pro version. Please contact us if you run into any difficulties.

### 1.3.2 — 2024-11-10

Thank you to everyone who has downloaded Watch Gear Calculator and for your fantastic feedback. As promised, I have now added the ability to save and share calculations. Furthermore, you no longer need to know RPMs for 2nd or 4th wheels. You can now use just the BPH. And for those odd occasions when you are not 100% sure of a movement’s BPH, you can calculate it from the RPM of 2nd or 4th wheels.

A new setup screen guides you to setup your calculation based on what you do or do not know to make sure you are working as efficiently as possible.

The interface layout is much improved with cells that refer to more than one wheel, ie the teeth of one and the leaves of the next, positioned as such.

Thanks again for supporting this little project. I really hope this app helps you. Please reach out with ideas and suggestions as always.

### 1.02 — 2024-10-22

No release notes.

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## More apps by David Margolis

- [Nyblit 2: To-Do List & Planner](https://appshunter.io/ios/app/nyblit-2-to-do-list-and-planner/id6752837986)

All apps by David Margolis: https://appshunter.io/developer/1773372938

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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 2026-08-22.*