The best companion app for your mechanical watch.


• Set your watch precisely with a full-screen atomic clock.
• Track your watches’ accuracy over time with beautiful charts. Trend lines tell you how your watch is performing and let you know when it’s time for service.

Atomic Clock

The “Atomic Clock” tab is a precise clock you can use to set your mechanical watch to the second.


On the “Watches” tab, add and name each of the watches you want to track. Tap “Add Point” to add a measurement. Wait until your watch’s hands match what’s shown on the screen, then tap the screen. This will add a point to the chart, recording if your watch was ahead or behind, and by how much. Repeat this over time and you will start to see trend lines with an estimate of your watch’s accuracy.

If your watch gains or loses 3s/day or less... congratulations! You have a chronometer-quality piece. If your watch gains or loses more than 60s/day, it might be in need of service.

When adding a measurement, if your watch is ahead of the time shown on the screen, or significantly behind, you can adjust the target time to get closer. Use the -5 and +5 buttons until the hands are slightly ahead compared to your watch, then wait for your watch to catch up, and tap.


• When you add a point, the hands on the screen automatically jump ahead by 5 seconds. This is so you can add a new point 5 seconds later. Do this a few times in a row to increase the accuracy of your measurements.
• To remove a point, force-press or long-tap on it to bring up a delete button.
• If you have iCloud enabled, you can find raw data, with all your measurements, in your iCloud Drive. The data is in the standard CSV format, supported by Excel, Numbers, Google Sheets, and many other apps.

What’s New

Version 1.8

Phone screen now stays awake while on the clock screen.

Ratings and Reviews

4.2 out of 5
10 Ratings
10 Ratings
derekbot3000 ,

Beautiful app, look forward to future updates and feature

I’ve been searching for a great app to measure my mechanical watch accuracy. After trying a couple other top apps in the store I was excited to see this one appear.
Looks perfect on the iPhone Xs screen. Fits in perfectly with iOS’s style but looks unique in its own right.
It is rather minimal in features but the core functions (atomic clock, watch accuracy tracking is great). I hope some more robust feature can be added in the future. I would love to be able to edit mistake points on the graph, add more information on the watch like year or purchase date, iCloud sync, and notification reminder if desired.
Great app! Thanks!
[Update] iCloud sync and deleting points have been added since first review. Great support from devs. Thanks!!

Developer Response ,

Thanks for the kind words! We’ve added iCloud sync and the option to delete points in the graph. Please try the new version and let us know how you like it. (P.S. - Reminders are coming soon!)

koffee66 ,

Beautifully designed and thoughtful app

The app is thoughtfully designed and beautiful to look at. The haptics on the ticking second hand are a nice touch. Good set of functionality and excited to see where the developer takes it. Fills a real niche in the market.

Developer Response ,

Thanks! We’re flattered. New features are coming soon! Feel free to email us with any other ideas or suggestions.

masnopik ,

Great simple app to measure watch accuracy

This app has helped me tracking my watch accuracy with simple steps.

Super easy to use. Well thought design, and app has crafted beautifully.

Thanks for making this app.


Rational Creation LLC
18.5 MB

Requires iOS 9.0 or later. Compatible with iPhone, iPad, and iPod touch.



Age Rating
Rated 4+
© 2018 Rational Creation LLC


  • Family Sharing

    With Family Sharing set up, up to six family members can use this app.

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