Resolution setting to achieve readability series 1: Different media—fonts size on screen and print

How do you remove fonts size on print to screen to achieve readability?

Fonts size is different between screen and paper. Why?
How do you measure both sizes?
How do you exchange them?
What are the standard resolution/fonts size for them to achieve good readability?

The computer screen is not a piece of paper and is not read at the same distance or orientation as print on paper. We do not notice that fonts size is different setting on both of them because they all designed by people-oriented considering.

Font sizes in inches are fine on a piece of paper but meaningless on a PC screen where the size of anything is measured in pixels.
Inches on a piece of paper are physical inches which using point when output on print, and Inches on a screen are logical inches that the unit is pixels. See the explanation of logical inch.
A formula given by the emdpi.com make a connection of inches and pixels

font size in pixels = font size in inches × screen dpi

For example:

Screen dpi and image or scanner dpi are different concepts.

The common term of DPI is a fixed number for a given printer. It is a phisical characteristic of a printer, and also known as the maximum resolution that a printer is capable of. Low-end printers have lower DPI while high-end printers have higher DPI.
When printing it is important to make sure that the DPI is higher or equal to the PPI. If the DPI is lower than the PPI the printer will not be able to fully display the high resolution of the photo.
300 dpi is going to look fine, 600 dpi will look great, 1,200 dpi is excellent, and once you get above 1,200 dpi, it’s going to be nearly impossible to see any difference in whatever you’ve printed.
You might got question about “Is it same DPI requirement for both pics and text on print?” I don’t know, but from Scott Elli's answer it would be the same for text.

Screen dpi would be more sense if we called “screen ppi”( pixels per inch). It has one purpose, and one purpose only, and that is to transform screen inches into screen pixels. It has nothing to do with physical inch measurements or screen images. The dots in screen dots per inch are pixels, but the inches are logical inches and not physical inches. see here
There is some relationship between Text Size and Screen Resolution. A survey of Browser Text Size settings from clickdensity shows:
1. The vast majority of visitors (99.7%) use default (Medium) text size settings.
2. Approximately twice as many visitors (0.2%) increase their text size than decrease their text size (0.1%).
3. Users with very low (640 x 480) or very high (larger than 1600 x 1200) screen resolutions are at least twice as likely to change their text size settings (compared to users with resolutions from 800 x 600 to 1280 x 1024).