IPHONE FOLD DIMENSIONS: HERE'S HOW THE FOLDABLE IPHONE SIZES UP NEXT TO THE IPHONE 18 PRO

Summary from the TLDR Design newsletter

Leaked dummy units shared by Sonny Dickson suggest Apple's foldable iPhone will be wider and shorter than Pro Max models when closed, but unfold into a ~7.8-inch display with a usable area closer to an iPad mini, emphasizing a better landscape experience despite a potentially awkward closed form. It's expected to feature an almost invisible crease, use Touch ID instead of Face ID due to space constraints, and be under 5 mm thick when unfolded but slightly thicker than current Pro models when folded.