CSS Units
Posted: Fri Oct 27, 2023 8:24 am
CSS Units
CSS Units
CSS has several different units for expressing a length.
Many CSS properties take "length" values, such as width, margin, padding,
font-size, etc.
Length is a number followed by a length unit, such as 10px,
2em, etc.
Example
Set different length values, using px (pixels):
h1 { font-size: 60px;}p { font-size: 25px;
line-height: 50px;}
Try it Yourself »
Note: A whitespace cannot appear between the number and the unit. However, if the value is
0, the unit can be omitted.
For some CSS properties, negative lengths are allowed.
There are two types of length units: absolute and relative.
Absolute Lengths
The absolute length units are fixed and a length expressed in any of these will appear as exactly that size.
Absolute length units are not recommended for use on screen, because screen sizes vary so much.
However, they can be used if the output medium is known, such
as for print layout.
Unit
Description
cm
centimeters
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mm
millimeters
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in
inches (1in = 96px = 2.54cm)
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px *
pixels (1px = 1/96th of 1in)
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pt
points (1pt = 1/72 of 1in)
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pc
picas (1pc = 12 pt)
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* Pixels (px) are relative to the viewing device. For low-dpi devices, 1px is one device pixel (dot) of the display. For printers and high resolution
screens 1px implies multiple device pixels.
Relative Lengths
Relative length units specify a length relative to another length property.
Relative length units scale better between different rendering mediums.
Unit
Description
em
Relative to the font-size of the element (2em means 2 times the size of the current font)
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ex
Relative to the x-height of the current font (rarely used)
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ch
Relative to width of the "0" (zero)
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rem
Relative to font-size of the root element
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vw
Relative to 1% of the width of the viewport*
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vh
Relative to 1% of the height of the viewport*
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vmin
Relative to 1% of viewport's* smaller dimension
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vmax
Relative to 1% of viewport's* larger dimension
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%
Relative to the parent element
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Tip: The em and rem units are practical in creating perfectly
scalable layout!* Viewport = the browser window size. If the viewport is 50cm
wide, 1vw = 0.5cm.
Browser Support
The numbers in the table specify the first browser version that fully supports the
length unit.
Length Unit
em, ex, %, px, cm, mm, in, pt, pc
1.0
3.0
1.0
1.0
3.5
ch
27.0
9.0
1.0
7.0
20.0
rem
4.0
9.0
3.6
4.1
11.6
vh, vw
20.0
9.0
19.0
6.0
20.0
vmin
20.0
12.0
19.0
6.0
20.0
vmax
26.0
16.0
19.0
7.0
20.0
★
+1
Reference: https://www.w3schools.com/css/css_units.asp
CSS Units
CSS has several different units for expressing a length.
Many CSS properties take "length" values, such as width, margin, padding,
font-size, etc.
Length is a number followed by a length unit, such as 10px,
2em, etc.
Example
Set different length values, using px (pixels):
h1 { font-size: 60px;}p { font-size: 25px;
line-height: 50px;}
Try it Yourself »
Note: A whitespace cannot appear between the number and the unit. However, if the value is
0, the unit can be omitted.
For some CSS properties, negative lengths are allowed.
There are two types of length units: absolute and relative.
Absolute Lengths
The absolute length units are fixed and a length expressed in any of these will appear as exactly that size.
Absolute length units are not recommended for use on screen, because screen sizes vary so much.
However, they can be used if the output medium is known, such
as for print layout.
Unit
Description
cm
centimeters
Try it
mm
millimeters
Try it
in
inches (1in = 96px = 2.54cm)
Try it
px *
pixels (1px = 1/96th of 1in)
Try it
pt
points (1pt = 1/72 of 1in)
Try it
pc
picas (1pc = 12 pt)
Try it
* Pixels (px) are relative to the viewing device. For low-dpi devices, 1px is one device pixel (dot) of the display. For printers and high resolution
screens 1px implies multiple device pixels.
Relative Lengths
Relative length units specify a length relative to another length property.
Relative length units scale better between different rendering mediums.
Unit
Description
em
Relative to the font-size of the element (2em means 2 times the size of the current font)
Try it
ex
Relative to the x-height of the current font (rarely used)
Try it
ch
Relative to width of the "0" (zero)
Try it
rem
Relative to font-size of the root element
Try it
vw
Relative to 1% of the width of the viewport*
Try it
vh
Relative to 1% of the height of the viewport*
Try it
vmin
Relative to 1% of viewport's* smaller dimension
Try it
vmax
Relative to 1% of viewport's* larger dimension
Try it
%
Relative to the parent element
Try it
Tip: The em and rem units are practical in creating perfectly
scalable layout!* Viewport = the browser window size. If the viewport is 50cm
wide, 1vw = 0.5cm.
Browser Support
The numbers in the table specify the first browser version that fully supports the
length unit.
Length Unit
em, ex, %, px, cm, mm, in, pt, pc
1.0
3.0
1.0
1.0
3.5
ch
27.0
9.0
1.0
7.0
20.0
rem
4.0
9.0
3.6
4.1
11.6
vh, vw
20.0
9.0
19.0
6.0
20.0
vmin
20.0
12.0
19.0
6.0
20.0
vmax
26.0
16.0
19.0
7.0
20.0
★
+1
Reference: https://www.w3schools.com/css/css_units.asp