How can you format your iPhone?

If you want to format it with out using iTunes then go to setting on your iphone then to general then to reset then select erase all content and settings it should ask you to enter your pass code then it will make sure with you that you really want to format your iphone to its original state and after a few minutes your done.

Here is a way about how to format iphone. Settings--->General--->Reset--->Erase All Content and Settings and wait for the iphone to format itself. Before format your iphone, you'd better backup your data.