Calculator online for translation ratios (px, %, pt, em).
Pixels (px) have a fixed size of the units used on the screens of different devices, one pixel is one dot on the computer screen (this is the smallest element of your screen resolution).
The problem with using (px) is that these units do not allow you to change the scale for the visually impaired readers or mobile devices.
Percents (%), units of measurement (%) is similar to (em), except for a few differences.
The current font-size is 100% (i.e. 12pt = 100%).
If you use (%), your text becomes fully scalable for mobile devices and the convenience of the user.
Points (pt) are used in the print media and one (pt) is equal to 1/72 of an inch, (pt) the same as (px) have a fixed size.
Ems (em), a scalable unit that is used in web documents, (em) is equal to the current font-size, for example, if the font-size in the document is 12pt, 1em is equal to 12pt, (em) scalable in nature, so 2em would equal 24pt, 0.5 em would equal 6pt, etc.