You can find the iOS version currently installed in your iPhone, iPod Touch, or iPad by checking your device's Settings, or via iTunes.

Using the Settings screen to determine your iOS version:

• Turn on your device and tap Settings.
• Select General.
• Tap on About. The iOS version installed on your device will be shown next to "Version."

Using iTunes to determine your iOS version:

• Open iTunes on your computer and connect your device using the USB cable. If you do not have iTunes on your computer, you can download it from the Apple website: http://www.apple.com/itunes/download/
• Once your iOS mobile device shows up under Devices on the left side of the iTunes window, select your device in iTunes.
• The iOS version installed on your device will be shown next to "Software Version" in the Summary tab on the right side of the iTunes window.

Related Article:

How do I install the latest iOS version on my iPhone, iPod touch, or iPad?