According to a video comparison by 9to5Mac, Apple’s official dimensions for the folding iPhone Duo reveal that its unfolded width is nearly identical to the height of the iPhone 18 Pro Max. When opened, the Duo measures 6.48 inches wide and 4.64 inches tall. By contrast, the iPhone 18 Pro Max is 6.43 inches tall and 3.07 inches wide — making the Duo’s width almost exactly the same as the Pro Max’s height.
The Duo’s unfolded size gives it the largest display ever in an iPhone, exceeding the Pro Max’s screen. The device is Apple’s first folding iPhone, and the company earlier offered a $19 replaceable cover layer to address concerns about the crease. The dimensions highlight how differently the two devices handle screen real estate: the Duo opens to a roughly square canvas, while the Pro Max remains a tall, narrow slab.