CSS单位

cap

Represents the "cap height" (nominal height of capital letters) of the element’s font.

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.

ex

Represents the x-height of the element's font. On fonts with the "x" letter, this is generally the height of lowercase letters in the font; 1ex ≈ 0.5em in many fonts.

ic

Equal to the used advance measure of the "水" (CJK water ideograph, U+6C34) glyph found in the font used to render it

.lh

Equal to the computed value of the line-height property of the element on which it is used, converted to an absolute length.

rem

Represents the font-size of the root element (typically <html>). 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).

rlh

Equal to the computed value of the line-height property on the root element (typically <html>), converted to an absolute length. When used on the font-size or line-height properties of the root element, it refers to the properties' initial value.

vh

Equal to 1% of the height of the viewport's initial containing block.

vw

Equal to 1% of the width of the viewport's initial containing block.

vi

Equal to 1% of the size of the initial containing block, in the direction of the root element’s inline axis.

vb

Equal to 1% of the size of the initial containing block, in the direction of the root element’s block axis.

vmin

Equal to the smaller of vw and vh.

vmax

Equal to the larger of vw and vh.