See the chart below to determine whether you can upgrade your device and to what you can upgrade. If you do not have a Software Update option present on your iDevice, then you are trying to upgrade to iOS 5 or higher. You will have to connect your device to your computer and open iTunes to update.
iPhone, iPod Touch, and iPad iOS Compatibility Chart
Device iOS Version
iPhone 1 iOS 3.1.3
iPhone 3G iOS 4.2.1
iPhone 3GS iOS 6.1.x
iPhone 4 iOS 7.1.x
iPhone 4S iOS 9.x.x
iPhone 5 iOS 10.x.x
iPhone 5c iOS 10.x.x
iPhone 5s iOS 11.x.x
iPhone 5se iOS 11.x.x
iPhone 6 iOS 11.x.x
iPhone 6 Plus iOS 11.x.x
iPhone 7 iOS 11.x.x
iPhone 7 Plus iOS 11.x.x
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iPod Touch 1 iOS 3.1.3
iPod Touch 2 iOS 4.2.1
iPod Touch 3 iOS 5.1.1
iPod Touch 4 iOS 6.1.x
Pod Touch 5 iOS 9.x.x
iPod Touch 6 iOS 11.x.x
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iPad 1 iOS 5.1.1
iPad 2 iOS 9.x.x
iPad 3 iOS 9.x.x
iPad 4 iOS 10.x.x
iPad 5 iOS 11.x.x
iPad Pro 12.9” iOS 11.x.x
iPadPro 9.7” iOS 11.x.x
iPad Mini & Mini Retina iOS 11.x.x
iPad mini 2 iOS 11.x.x
iPad mini 3 iOS 11.x.x
iPad mini 4 iOS 11.x.x
iPad Air iOS 11.x.x
iPad Air 2 iOS 11.x.x
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Select the method most appropriate for your situation.
Upgrading iOS
1. How to update your iPhone, iPad, or iPod Touch
2. iPhone Support
3. iPod Touch Support
4. iPad Support
a. Updating Your iOS from iOS 5
Tap Settings > General > Software Update
If an update is available there will be an active Update button. If you are current,
then you will see a gray screen with a message saying your are up to date.
b. If you are still using iOS 4— Updating your device to iOS 5 or later.
c. Resolving update problems
1. iOS - Unable to update or restore
2. iOS- Resolving update and restore alert messages