CSS units and values

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CSS3 Unit and Values spec.

The contents of my CSS pages and browser compatibility.

This is the desktop table. See also the mobile table.

Last major update on 14 March 2013.

I'm writing a CSS book.

Font-dependent units

Selector IE7 IE8 IE9 IE10 FF 19 Win FF 19 Mac Safari 6.0.2 Mac Chrome 25 Win Chrome 25 Mac Yandex 1.5 Mac Opera 12.14 Win Opera 12.14 Mac
ch unit
Width of the character “0” in the current font. 		No Yes Yes No No No
em unit
Equal to the font size in pixels 		Yes Yes Yes Yes Yes
ex unit
Width of the “x” character OR equal to half an em 		Yes Yes Yes Yes Yes
rem unit
Equal to the font size of the HTML element 		No Yes Yes Yes Yes Yes

Absolute units

Selector IE7 IE8 IE9 IE10 FF 19 Win FF 19 Mac Safari 6.0.2 Mac Chrome 25 Win Chrome 25 Mac Yandex 1.5 Mac Opera 12.14 Win Opera 12.14 Mac
cm unit
1 in = 2.54 cm 		Yes Yes Yes Yes Yes
in unit
1 in = 96 px 		Yes Yes Yes Yes Yes
mm unit
10 mm = 1 cm 		Yes Yes Yes Yes Yes
pc unit
1 pc = 12 pt 		Yes Yes Yes Yes Yes
pt unit
1 in = 72 pt 		Yes Yes Yes Yes Yes
px unit
ROOT UNIT 		Yes Yes Yes Yes Yes

Viewport units

Static: The browser correctly sizes the elements on page load, but does not update them when the page is resized.

Selector IE7 IE8 IE9 IE10 FF 19 Win FF 19 Mac Safari 6.0.2 Mac Chrome 25 Win Chrome 25 Mac Yandex 1.5 Mac Opera 12.14 Win Opera 12.14 Mac
vh and vw units
Percentages of the viewport width 		No Yes Yes Static Static No
vmax unit
Percentages of the larger of viewport width or height 		No Yes No No No
vmin unit
Percentages of the smaller of viewport width or height 		No Yes Yes Static Static No
Selector IE7 IE8 IE9 IE10 FF 19 Win FF 19 Mac Safari 6.0.2 Mac Chrome 25 Win Chrome 25 Mac Yandex 1.5 Mac Opera 12.14 Win Opera 12.14 Mac

Values

Selector IE7 IE8 IE9 IE10 FF 19 Win FF 19 Mac Safari 6.0.2 Mac Chrome 25 Win Chrome 25 Mac Yandex 1.5 Mac Opera 12.14 Win Opera 12.14 Mac
calc()
To perform calculations in CSS 		No Yes Yes -webkit- -webkit- No

Not supported

These values are not supported in any browser.