There are not a few developers who can't remember the pixel size of iOS app icons like me. I often need to query the app sizes on different devices. In order to make it easier for me and everyone, I made the following chart for your reference.
What are the pixel sizes of iPhone, ipodtouch, and general application icons?
The iPhone and ipodtouch applications require all the icon pixels of the general application. You may want to know why the iPhone application requires the icon of the iPad application, because an iPhone application can also run on the iPad.
On the contrary, the iPad app cannot run on the iPhone, so the iPad app has its own icon pixel.
Required icon:
Appstore icon: 1024x1024 pixels
IPhone home screen icons: 57x57, 114x114 (retina) pixels
IPad home screen icons: 72X72, 144x144 (retina) pixels
Optional icons:
IPhone, ipadsettings, iphonespotlightsearchresults: 29 × 29, 58 × 58 (retina) pixels
Ipadspotlightsearchresults: 50 × 50, 100 × 100 (retina) pixels
What kind of icons are needed for iPad apps.
Because only apps for iPad can no longer run on the iPhone, you don't need so many icons.
Required icons:
Appstore icon: 1024x1024 pixels
IPad home screen icons: 72X72, 144x144 (retina) pixels
Optional icons:
Ipadsettings: 29 × 29and58 × 58 (retina) pixels
Ipadspotlightsearchresults: 50 × 50and100 × 100 (retina) pixels