Why does my iPhone battery jump from 30 to 1 percent?

Your iPhone battery usually jumps from 30% to 1% because the battery estimate no longer matches the battery’s real charge. The most common causes are battery aging, cold temperatures, or a software/reporting glitch.

What to check:

• Go to Settings > Battery > Battery Health & Charging
• If Maximum Capacity is below about 80%, the battery is likely worn and replacement often fixes it
• If it’s in cold weather, warm the phone back to room temperature
• Update iOS in Settings > General > Software Update

One thing that can help: a single calibration cycle — let it run down until it turns off, then charge uninterrupted to 100%, and leave it on the charger a bit longer once full. Don’t do this often.

If it keeps happening after that, the battery is probably aging even if the percentage still looks decent.