Turn Your MacBook into a Digital Weighing Scale with TrackWeight

Yes, your MacBook can now weigh things no joke. Thanks to a new macOS app called TrackWeight, you can transform your MacBook’s Force Touch trackpad into a surprisingly accurate digital weighing scale. Created by Canadian developer Krish Shah, the app uses Apple’s built-in pressure-sensitive technology to weigh small objects without any external hardware.

How It Works

Using TrackWeight is simple. Place your finger on the trackpad and then gently rest a lightweight object on it. The app reads the pressure data and converts it directly into grams. Your finger needs to stay in contact with the pad, as the sensor relies on capacitance to function correctly.

This clever tool works only on Force Touch-enabled MacBooks from 2015 or later and runs locally on the device.

The Tech Behind TrackWeight

TrackWeight is powered by Open Multi-Touch Support, a macOS library created by developer Takuto Nakamura. This library allows access to low-level touch sensor data, including pressure, angle, and touch position data typically hidden by Apple’s APIs.

Shah’s app taps into this data stream and uses it to measure force and convert it to weight. Calibration was straightforward: he placed his MacBook on a standard scale, added small items while pressing the trackpad, and compared the readings. Since macOS already labels some pressure values in grams, no conversion was necessary. According to Shah, the app can handle weights up to 3.5 kilograms with decent accuracy.

Real-World Testing

In a series of demo videos on X (formerly Twitter), Shah showcased his experiments by comparing TrackWeight’s output with a regular scale’s display. The results? Surprisingly close. He describes the Force Touch trackpad as essentially a pressure pad with haptic feedback, making it ideal for experimental applications like this.

Know the Limitations

TrackWeight is experimental and not meant to replace commercial digital scales. Here are a few caveats:

• Your finger must stay on the trackpad for accurate readings.
• Metal objects can give false results unless placed over paper or cloth.
• The small size of the trackpad limits the types and sizes of items you can weigh.
• Placing very heavy objects on the trackpad may damage your MacBook. 

How to Get TrackWeight

TrackWeight is open-source, licensed under MIT, and available on GitHub. To use it:

• You need macOS 13 or later.
• Your MacBook must support Force Touch.
• You’ll need Xcode to build and run the app.
• App Sandbox must be disabled due to the app’s need for low-level system access. 

TrackWeight is for educational and demonstration purposes only, not for critical or professional weighing tasks.