I am aware that the phrase “life hack” can sometimes be shorthand for “useless tip.” The jokes are decades old at this point, something I try to be aware of when I write an article. So let me be clear: I do not think you should use your MacBook as a scale. You can, though.
Ontario-based developer Kris Shah made an app that turns any Mac trackpad into a scale. This isn’t a good idea in the kitchen, mostly because you don’t want to spill ingredients on your expensive laptop. But the app is called TrackWeight—it’s ridiculous, and I love it.
Using Trackweight requires holding a finger lightly on the trackpad (this is because your Mac doesn’t activate the trackpad unless it’s being touched by a finger or something else with capacitance). The idea is to rest your finger in such a way where you’re not pushing down at all—I had the most luck just barely holding my finger over the trackpad but mostly resting it on the laptop. You can hit the spacebar with your other hand to reset the weight to zero, if you want, or you can just put your object onto the trackpad to measure it.
Credit: Justin Pot
I tested this with a few objects, mostly notably a bowl of blueberries. The result was within a few grams of my kitchen scale.
Credit: Justin Pot
I also tested this with a standalone Magic Trackpad—it worked just as well, and is possibly slightly more practical as a scale (but still not really practical at all).
So why does this work? The Mac Trackpad has a built-in pressure sensor, mostly used to detect how hard you’re pressing for features like Force Touch. When you press and hold on your Trackpad to trigger the “Look Up” tool and other features, your Mac is using a pressure sensor to detect that you’re pressing harder.
According to the developer, there’s a hidden API on the Mac that makes it possible for applications to detect the amount of pressure currently being applied to the track pad, and that’s what’s used to calculate the weight of the object. It’s a fascinating hack, and a demonstration of the unexpected technology embedded in modern laptops.
