The website ChargerLAB has tested the iPhone 17 Pro Max's USB-C charging speeds with a variety of Apple's chargers, from 18W to 140W.
The device reached a peak charging speed of around 36W with the following Apple chargers:
For comparison, the iPhone 16 Pro Max can reach a peak charging speed of around 30W, so the iPhone 17 Pro Max can charge a bit faster.
The smaller iPhone 17 Pro can likely reach the same 36W peak.
minutes with a compatible charger, including the 40W Dynamic Power Adapter with 60W Max. For comparison, the iPhone 16, iPhone 16 Pro, and iPhone 16 Pro Max can be charged up to 50% in 30 minutes with a compatible charger.
Apple's 40W Dynamic Power Adapter with 60W Max is available to order in the U.S., Canada, China, Japan, Mexico, Taiwan, and the Philippines.
Keep in mind you also need an appropriate USB-C cable for fast-charging capabilities, with the most basic or cheap options sometimes not supporting enough power delivery. If you are unsure, the USB-C cable included in the box with iPhones does the trick.
Source: Macrumors