If you use a third party software like iMazing, it will give you the battery capacity of an iPhone. It says the design capacity for the 16 Pro Max is 4630 ma. Some sources claim it is 4685 ma. Apple always seems to give you a little more battery capacity than stated so that it shows 100% battery health for a longer time as it degrades. My new 16 Pro Max is showing an effective total capacity of 4837 ma, which is 104.5% of the rated design capacity. Same thing happened with my 14 Pro Max and the battery health was still at 100% after 2 years and careful charging to about 80%. So its not surprising why people are getting really long battery life with the 16 Pro Max.