Leak Suggests iPhone 18 Pro Max Will Be Thicker And Heavier To Fit Bigger Battery

Apple’s next big flagship may get physically bigger in ways users will notice. A new leak out of China suggests the upcoming iPhone 18 Pro Max will carry a much larger battery, with a trade-off in added thickness and weight compared to the current model.

According to details shared by well-known Chinese leaker Ice Universe on Weibo, the iPhone 18 Pro Max is said to feature a 5,500mAh battery. That capacity would be “significantly larger,” as first highlighted in recently surfaced Chinese regulatory filings, and is expected to translate into longer battery life.

The reported upgrade, however, isn’t coming for free in design terms.

Ice Universe claims the 5,500mAh pack “comes at the cost” of a 240-gram device with a 9mm thick body. For comparison, Apple’s current large flagship, the iPhone 17 Pro Max, is 8.75mm thick and weighs 233 grams. If the leak is accurate, the iPhone 18 Pro Max would be 0.25mm thicker and 7 grams heavier than its predecessor.

Those changes might sound incremental on paper, but they would be noticeable in a device that is already among the biggest mainstream smartphones. A move to 240 grams would also put the iPhone 18 Pro Max back in the weight class of Apple’s heaviest phone to date: the iPhone 14 Pro Max, which still holds the record at 240 grams. In other words, the new model could match that peak weight rather than exceed it.

There may be more than just the battery contributing to the potential weight bump. As noted by MacRumors, Apple has reportedly adopted a new type of vapor chamber cooling system that uses stainless steel in the iPhone 18 Pro Max. A stainless steel-based design could also add grams, even if it improves thermal performance under sustained workloads.

The leak and regulatory hints focus squarely on the 18 Pro Max, leaving the smaller iPhone 18 Pro more of an open question. There’s no confirmed information on the weight or dimensions of the 18 Pro at this stage. Its battery is reportedly only “a little larger” than before, which might mean any change in thickness and weight is less dramatic than on the Max model, but the exact numbers aren’t yet known.

Beyond the Pro line, Apple is also rumoured to be preparing an iPhone Ultra model, expected to launch alongside the Pro devices in September. That device is described as having a foldable design, which by its nature is likely to make it the heaviest new iPhone in the line-up. However, there are no specific figures yet on its weight, dimensions, or battery capacity.

For now, the picture that’s emerging is of an iPhone 18 Pro Max that leans into battery longevity and potentially improved cooling, even if it means nudging the device back toward the weight of Apple’s bulkiest previous flagship.