...it's big. Look at that photo. So how big is it? The phone has a 6.4 inch screen, which is as you can see, makes it look more like a mini tablet than a phone. That's bigger than any iPhone, and even the Samsung Galaxy S4, which has a 5 inch screen. Sony claims it is the world’s largest full HD smartphone display. As we've found time and time again though, just because something is the "world's largest" doesn't necessarily make it a great phone.