The em is simply the font size. In an element with a 2in font, 1em thus means 2in. Expressing sizes, such as margins and paddings, in em means they are related to the font size, and if the user has a big font (e.g., on a big screen) or a small font (e.g., on a handheld device), the sizes will be in proportion.Click to see full answer. Also to know is, what is the use of EM in CSS?“Ems” (em): The “em” is a scalable unit that is used in web document media. An em is equal to the current font-size, for instance, if the font-size of the document is 12pt, 1em is equal to 12pt. Ems are scalable in nature, so 2em would equal 24pt, . 5em would equal 6pt, etc.Also, what is em and px in CSS? EM is relative to the current font size of the element (2em means 2 times the size of the current font). So, If the font size of body is 16 pixels, then 150% will be 24 pixels (1.5 * 16), and 2em will be 32 pixels (16 * 2). Look at CSS Units for more measurement units. Subsequently, one may also ask, what is EM in CSS? In CSS, an em unit is equal to the computed font-size for the element to which the em is applied. If no font size is defined anywhere in the CSS, the em unit will be equal to the browser’s default font size for the document, which is usually 16px.Why is em better than PX?The main reason for using em or percentages is to allow the user to change the text size without breaking the design. If you design with fonts specified in px, they do not change size (in IE 6 and others) if the user chooses text size – larger. This is very bad for users with visual handicaps.