BackgroundSize

This keyword specifies that the background image should be scaled to be as large as possible while ensuring both its dimensions are less than or equal to the corresponding dimensions of the background positioning area.

This keyword specifies that the background image should be scaled to be as small as possible while ensuring both its dimensions are greater than or equal to the corresponding dimensions of the background positioning area.

Wrap the provided expression in CSS calc() function.

ch represents the width, or more precisely the advance measure, of the glyph "0" (zero, the Unicode character U+0030) in the element's font.

em represents the calculated font-size of the element. If used on the font-size property itself, it represents the inherited font-size of the element.

1 pt is 4/3 of a pixel.

Pixels

rem represents the font-size of the root element (typically ). When used within the root element font-size, it represents its initial value (a common browser default is 16px, but user-defined preferences may modify this).

1 vh is equal to 1% of the height of the viewport's initial containing block

1 vmax is equal to the larger of 1 vw and 1 vh

1 vmin is equal to the smaller of 1 vw and 1 vh

1 vw is equal to 1% of the width of the viewport's initial containing block