Upgrading to the iPhone 18 Pro? Almost all older cases will survive the jump because Apple kept its exterior dimensions identical to the iPhone 17 Pro. Apple lists both generations of the smaller Pro at 5.91 inches tall, 2.83 inches wide, and 0.34 inch deep. In metric measurements, each phone is 150 mm by 71.9 mm by 8.75 mm.

The same applies to the larger models. Both iPhone 17 Pro Max and iPhone 18 Pro Max measure 6.43 inches tall, 3.07 inches wide, and 0.34 inch deep, or 163.4 mm by 78 mm by 8.75 mm. Those measurements come directly from Apple's technical specifications and its support pages for iPhone 17 Pro and Pro Max.

Unlike some annual updates, there isn't even a fraction-of-a-millimeter difference between the corresponding models. The matching height, width, and depth confirm that an older case can wrap around the new chassis. Apple also retained the Action button, volume controls, side button, Camera Control, USB-C port, and full-width camera platform introduced with the iPhone 17 Pro.

The new models do bring substantial internal and camera changes. The iPhone 18 Pro adds the A20 Pro chip, redesigned cooling, and a 48MP main camera with variable aperture, but Apple fit those upgrades inside the existing exterior dimensions. Apple hasn't formally promised that cases are interchangeable, however. Its new silicone and Tech Woven case listings identify only iPhone 18 Pro or iPhone 18 Pro Max under compatibility, while the older cases continue to list only their matching iPhone 17 model.