How to Use Your iPhone's Stopwatch and Timer
Your iPhone can serve as a stopwatch and timer. These features, which are both available through the Clock application, work like a conventional stopwatch and timer.
Stopwatch on Your iPhone
If you’re helping a loved one train for a marathon, your iPhone’s Stopwatch function can provide an assist. It’s accessible by tapping Stopwatch in the Clock application.
Just tap Start to begin the count and tap Stop at the finish line. You can also tap a Lap button to monitor the times between laps.
Your iPhone's Timer feature
Cooking a hard-boiled egg or Thanksgiving turkey? The iPhone comes to the rescue. Tap Timer (within the Clock app) and then rotate the hour and minute wheels until the time you have in mind is highlighted. Tap When Timer Ends to choose the ringtone that will signify that time’s up.
After you’ve set up the length of the timer, tap Start when you’re ready to begin. You can watch the minutes and seconds wind down on the screen if you want.
But if you’re doing anything else on the iPhone — admiring photos, say — you’ll hear the ringtone and see a Timer Done message on the screen at the appropriate moment. Tap OK to silence the ringtone.