You need to calibrate the Compass whenever you open the app. Calibration is accomplished by tilting the screen, which triggers the roll of a red ball, within a circle. Calibration is complete when a full circle is drawn.
Update: iPhone Compass calibration is done automatically as long as the proper iOS settings are used.
If you’re a newbie to the Compass app, or simply never spent enough time to learn how to properly calibrate it, here is how to do it. It’s an easy but very efficient trick that helps you to perform iPhone Compass calibration within a second!
360° Compass Calibration Move
Simply open the app and perform a single circular motion with the hand that holds the iPhone. If you’re right-handed you need to rotate your wrist 360° degrees from left to right. In the same time, use your fingers to tilt the device. Perform a backward-tilt in the first half of your wrist rotation and change towards an upward move during the final 180° degrees of your wrist rotation.
This might sound complicated, but I assure you that it looks very easy. Simply watch the video available below and you can see how to execute the motion and calibrate your iPhone’s Compass within one second.
Level Meter and InclinometerHere is another great tip for discovering all features of your iPhone’s built-in Compass app. After calibrating the Compass you can swipe left to activate a Level Meter. You can check any surface and see if it’s level, or how much adjustment there’s needed, to make it perfectly level.
You want more? Place your iPhone on its edge and you’ll transform it in an Inclinometer. You will be able to tell the inclination of a certain surface. You don’t have to be a constructor to use this feature. You can easily establish the incline of a ski slope, for example.
iPhone Compass Calibration Demo
Check this video to see how I easily calibrate the Compass of my iPgone 5s running iOS 7. Level and Inclinometers at work are also shown!
Related: How to use the stock Apple Watch Compass app, available for Series 5 models and later.