RationAle gives you a rough guess at your blood alcohol content (BAC) based on the drinks you’ve had recently. Keep a list of your favourite drinks, or just enter the amount of standard drinks directly.

The app is especially handy when you've got an Apple Watch: your can add drinks from the watch, and the complication will show you your current estimated BAC. You can use ‘time travel’ to spin the crown and get a rough idea of how your BAC is going to change over time.

RationAle uses approximations based on the Widmark formula to make a guess at your blood alcohol content, based on your height, weight and sex—these guesses are intended to give you an idea of how your body might react to alcohol, and should not be used in place of an actual breathalyser, or to make serious decisions about when to drive.

What’s New

Version 1.3.1

Bug fixes: fixed issue on first launch and text appearance in the settings tab.

Ratings and Reviews

Enzo__D ,

Great app

Useful app with a clean and intuitive interface. Charts would be a great addition!

KidGenius75 ,

I love this app.

And I'm not just saying that because I'm drunk.

KidGenius75 ,

I love this app.

And I'm not just saying that because I'm drunk.


Tom Charman
25.3 MB
Food & Drink
Requires iOS 11.0 or later. Compatible with iPhone, iPad and iPod touch.
Age Rating
You must be at least 17 years old to download this application.
Frequent/Intense Alcohol, Tobacco or Drug Use or References
© 2018 Tom Charman


  • Family Sharing

    Up to six family members will be able to use this app with Family Sharing enabled.

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