The iPhone 6 Plus Go to product viewer dialog for this item.

For a static background, a 1080 x 1920 image matches the physical pixels perfectly.

Introduced in iOS 7, the Parallax Effect tilts the background as the phone moves to create a sense of depth. For this to work without showing black edges, wallpapers typically need to be slightly larger than the screen (e.g., roughly 15-20% extra padding) so the image has "room to move" behind the app icons. iPhone 6 & iPhone 6 Plus: A tale of scale - Six Colors

To fit the physical 1080p screen, the device automatically scaled this image down to