How to Determine the Physical Size of the Screen

The physical size of the screen on Android is
You can calculate using xdpi/ydpi and width/height (both pixels).
However, dpi is not always an accurate value.
For example, the dpi value of the Galaxy SIII is incorrect.

Is there any way to obtain the actual size directly?

Or
for Android TV or HDMI output. The size of the television itself, or
Is there a way to obtain a model ID to estimate its size?

Thank you for your cooperation.