Barometer

What it does

Shows live air pressure from your iPhone or iPad's built-in barometer, and your altitude from GPS.

What you need

• An iPhone or iPad with a barometer. This tool is not available on the web.
• For altitude, your current location (GPS). Saved and manual locations have no altitude.

How to use it

1. Open the tool. Pressure and Altitude update on their own.
2. To change the pressure unit, tap the info icon on the card and follow Settings > Units. Pressure can be shown in inHg (the default), hPa, or mmHg. Altitude uses your Imperial or Metric setting (ft or m).

Reading the results

• Pressure is the reading at your location, straight from the device's barometer.
• Altitude is your device's GPS elevation, typically accurate to within 10 to 20 m. If you are not using your current location, it shows a dash.
• On a device with no barometer, the tool says so and Pressure shows a dash. Altitude still works from GPS.