system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:How does screen resolution, size, and pixel density effect viewing?

I was doing some research into buying a new monitor and read that a standard monitor resolution of 1920 x 1080 means 1920 pixels horizontally and 1020 pixels vertically.  This would seem to mean that as you increase monitor size, you lose pixel density.  By my calculations, a 4k 55” TV monitor would have the same PPI (pixels per inch) as an HD (1920x1080) 27” computer monitor (about 80 PPI).  If I got a 19” computer monitor, it would have ~105 PPI.  The new Samsung smartphone has 560 PPI.  How does this work?  Why are larger monitors not manufactured with the same pixel density as smaller ones, and how does this affect viewing?
gpt
You forgot to take into account the viewing distance. Phones are held 20 centimeters from your face while TVs are normally viewed from a few meters away, and if you sit closer to the TV then a smaller TV is recommended.