The UIDevice class can help us do that like so:

    [super viewDidLoad];
	
    // lets detect the height of our screen here
    int height = [UIScreen mainScreen].bounds.size.height;
    int width = [UIScreen mainScreen].bounds.size.width;
    
    // share the news
    NSString *message = [[NSString alloc]initWithFormat:@"This screen is \n\n%i pixels high and\n%i pixels wide", height, width];
    NSLog(@"%@", message);

This will work fine in your View Controllers and App Delegate files.

I’ve got a full working demo project on GitHub: https://github.com/versluis/ScreenSize

Further Reading:

• http://stackoverflow.com/questions/12446990/how-to-detect-iphone-5-widescreen-devices
• http://stackoverflow.com/questions/5677716/how-to-get-the-screen-width-and-height-in-ios