how large can a I-Phone 15 pro max be enlarged ?

[f.22]

to what size can enlargement be made taken with I-phone 15 pro max ?

[SCL]

Any size you want. The key is the viewing distance.

[glen_h]

They have plenty of bits, so that isn't the problem.

At some point, there is the diffraction limit that you can't escape with tiny optics.

Shutterfly recommends 8 MP for the really huge prints, but 3MP is enough for even up to 20x30 inch:

https://support.shutterfly.com/s/article/Photo-Resolution-Tips-1

There are minimum where it won't even try that are somewhat smaller than those values.

[Ricochetrider]

I had a phone pic printed in a size of roughly 11 X 15 (I believe it to be 2:3 formatted on my phone which varies a bit from the same aspect ratio in 35mm!!!?).

Looking at the color print, you’d never know it’s a phone pic. Shot with (IIRC) the 11 version of the iPhone.  
 

Here’s the shot, it is actually one of my all time favorites! 

 

 

[Ken Katz]

Iphone 15's main camera is 48mp, and I believe the default images are set at 24mp, though you can shoot RAW and extract the full 48mp.  Even with the interpolated 24mp files, if the image is shot in good light, well within the phone's performance envelope (no computational tech used), I don't think there would be a significant limitation on printed image size, depending of course on viewing distance.  The more tech "tricks" needed, the faster the image will fall apart at larger magnification.

Not bad for a device that is always in most folks pockets and can order food, a taxi, and tell you the weather.