Measurements

px

A fixed, absolute measurement unit that does not scale with text size or screen size.

em

A relative unit based on the font size of the element itself (1em = current element's font-size).

rem

A relative unit based on the root HTML font size (1rem = html's font-size, usually 16px).

%

A fluid unit representing a percentage of the parent element’s size.

vw

A fluid unit equal to 1% of the viewport width.

vh

A fluid unit equal to 1% of the viewport height.

vmax

A fluid unit equal to 1% of the larger dimension of the viewport.

ch

A relative unit equal to the width of the "0" character in the current font.