Ever wonder why your iPhone vibrates whether or not it’s set to silent mode? The answer lies in a simple setting that—depending on the number of calls you have coming in—might be able to eke out a little extra battery life throughout the day. To change this, open up the Settings app, then tap on Sounds. On that page you’ll see two on/off toggles labeled “Vibrate”—one under Silent, and one under Ringer and Alerts. Simply go down to the latter one and make sure it’s set to off, and from then on your phone won’t vibrate unless it’s set to silent mode, saving you an extra bit of battery life and potentially saving it from rattling around and falling on the floor.