Units

For some CSS properties, negative lengths are
allowed. There are two types of length units:
absolute and relative.

Absolute Lengths

cm centimeters mm millimeters in inches (1in = 96px = 2.54cm) px* pixels (1px = 1/96th of 1in) pt points (1pt = 1/72 of 1in) pc picas (1pc = 12 pt)

Relative Lengths

em Relative to the font-size of the element (2em means 2 times the size of the current font) ex Relative to the x-height of the current font (rarely used) ch Relative to the width of the “0” (zero) rem Relative to font-size of the root element vw Relative to 1% of the width of the viewport* vh Relative to 1% of the height of the viewport* vmin Relative to 1% of viewport’s* smaller dimension vmax Relative to 1% of viewport’s* larger dimension % Relative to the parent element