For a few months now, I’ve been using PCalc as my only calculator and currency converter on iOS. As I wrote last year after the release of the app’s iOS 8 update, the ability to customize layouts and have fast access from Notification Center lets me launch PCalc quickly from anywhere and come up with my own custom buttons for frequent calculations and conversions.

I’ve been using PCalc on my Apple Watch for the past few days, and I’ve observed some interesting usage patterns in my early testing stage of the new device.¹ As you would expect, PCalc on Apple Watch presents a simplified layout with a number pad; anything you tap is displayed at the top of the screen and you can press firmly to bring up a menu to clear the current calculation, send it to PCalc on the iPhone, and undo.

Operations are hidden inside a special menu that is accessed by tapping a ‘More’ button: this is different from Calcbot’s reliance on Force Touch for basic operations, but it allowed developer James Thomson to cram more buttons in the additional screen – you can also tap the same button again to enter a tip calculation mode. I was initially put off by the decision to separate operators from the main view, but now I find PCalc’s primary view – with its large-enough tap targets and well delimited borders – to be clean and easy to use. As far as the concept of a calculator on your wrist goes, PCalc does the job fairly well.

What I wasn’t sure about was the very idea of using a calculator on a watch. But if my first week with PCalc on Apple Watch is of any indication, there’s one daily activity that greatly benefits from a wrist calculator: grocery shopping.

I buy fresh groceries with my girlfriend almost every day, and as we shop we want to make sure we stay within our budget for the week. As we add items to our cart, I enter prices in PCalc for iPhone; this has always required me to either shop with an iPhone in one hand (which is inconvenient for obvious reasons) or constantly pull the iPhone out of my pocket and put it back in. I shopped this way for years, and aside from the concern of dropping my phone when taking items off their shelves (which happened on a couple of occasions), I never loved the temptation of being lured by Twitter or Mail while I was buying groceries. I knew I didn’t like it and I was doing it anyway.

With this mindset and use case, switching to PCalc on Apple Watch while shopping has been an interesting experiment. Because it’s always there on my wrist, I don’t have to reach out for my iPhone; notifications are filtered by the Watch, so I can receive taps for important updates, see what they’re about, and make a conscious decision to deal with them later when I can use my iPhone or iPad again.

To enter the cost of a new item, I just need to raise my wrist, quickly double click the Digital Crown, tap numbers, and I’m done. The process requires about 5 seconds, and because my left hand isn’t holding an iPhone, I can still stop using the app and, say, help my girlfriend grab something because both hands are free and the Watch is on my wrist anyway.

This is an example of the convenience of Apple Watch: it’s always on you and it’s got the same apps you already use, but it’s not demanding or distracting as an iPhone can be.

I’m glad that PCalc is now on Apple Watch. PCalc fits my needs almost perfectly on iOS with its custom buttons and loud sound effects (I like clear, audible feedback) and I want to use the same app across my iPhone and Apple Watch. I’m already starting to see plenty of use cases for the Watch in my daily life; PCalc is making a small contribution by helping me buy fresh ingredients without having to use my iPhone.

PCalc 3.4 with Apple Watch support is available on the App Store.