width

Summary

The width CSS property specifies the width of the content area of an element. The content area is inside the padding, border, and margin of the element.

The min-width and max-width properties override width.

Initial value	`auto`
Applies to	all elements but non-replaced inline elements, table rows, and row groups
Inherited	no
Percentages	refer to the width of the containing block
Media	visual
Computed value	a percentage or `auto` or the absolute length
Animatable	yes, as a length, percentage or calc(); when both values are lengths, they are interpolated as lengths; when both values are percentages, they are interpolated as percentages; otherwise, both values are converted into a `calc()` function that is the sum of a length and a percentage (each possibly zero), and these `calc()` functions have each half interpolated as real numbers.
Canonical order	the length or percentage before the keyword, if both are present

Syntax

/* <length> values */
width: 300px;
width: 25em;

/* <percentage> value */
width: 75%;

/* Keyword values */
width: border-box;
width: content-box;
width: max-content;
width: min-content;
width: available;
width: fit-content;
width: auto;

/* Global values */
width: inherit;
width: initial;
width: unset;

Values

<length>

See <length> for possible units.

<percentage>

Specified as a <percentage> of containing block's width. If the width of the containing block depends on the width of the element, the resulting layout is undefined.

border-box

If present, the preceding <length> or <percentage> is applied to the element's border box.

content-box

If present, the preceding <length> or <percentage> is applied to the element's content box.

auto

The browser will calculate and select a width for the specified element.

max-content

The intrinsic preferred width.

min-content

The intrinsic minimum width.

available

The containing block width minus horizontal margin, border and padding.

fit-content

The larger of:

the intrinsic minimum width
the smaller of the intrinsic preferred width and the available width

Formal syntax

[<length> | <percentage>] && [border-box | content-box]? | available | min-content | max-content | fit-content | auto

Examples

Default width

p.goldie {
  background: gold;
}

<p class="goldie">The Mozilla community produces a lot of great software.</p>

Pixels and ems

.px_length {
  width: 200px;
  background-color: red;
  color: white;
  border: 1px solid black;
}

.em_length {
  width: 20em;
  background-color: white;
  color: red;
  border: 1px solid black;
}

<div class="px_length">Width measured in px</div>
<div class="em_length">Width measured in em</div>

Percentage

.percent {
  width: 20%;
  background-color: silver;
  border: 1px solid red;
}

<div class="percent">Width in percentage</div>

max-content

p.maxgreen {
  background: lightgreen;
  width: intrinsic;           /* Safari/WebKit uses a non-standard name */
  width: -moz-max-content;    /* Firefox/Gecko */
  width: -webkit-max-content; /* Chrome */
}

<p class="maxgreen">The Mozilla community produces a lot of great software.</p>

min-content

p.minblue {
  background: lightblue;
  width: -moz-min-content;    /* Firefox */
  width: -webkit-min-content; /* Chrome */
}

<p class="minblue">The Mozilla community produces a lot of great software.</p>

Specifications

Specification	Status	Comment
CSS Basic Box Model The definition of 'width' in that specification.	Working Draft	Added the `max-content`, `min-content`, `available`, `fit-content`, `border-box`, `content-box` keywords.
CSS Transitions The definition of 'width' in that specification.	Working Draft	Lists `width` as animatable.
CSS Level 2 (Revision 1) The definition of 'width' in that specification.	Recommendation	Precises on which element it applies to.
CSS Level 1 The definition of 'width' in that specification.	Recommendation	Initial definition

Feature	Chrome	Firefox (Gecko)	Internet Explorer	Opera	Safari (WebKit)
Basic support	(Yes)	1.0 (1.7 or earlier)	4	3.5	1.0 (85)
Animatability	?	16.0 (16.0)	?	?	?
`max-content`	22.0 -webkit 46.0 [1]	3.0 (1.9)-moz	?	15 -webkit	2.0 (421) (`intrinsic` value) 6.1 -webkit
`min-content`	22.0 [4] -webkit 46.0 [1]	3.0 (1.9) -moz	?	15 -webkit	2.0 (421) (`min-intrinsic` value) 6.1 -webkit
`available`	No support	3.0 (1.9) -moz	?	?	?^[1]
`fill-available`	22.0 -webkit	No support	?	?	6.1 -webkit
`fit-content`	22.0 [4] -webkit 46.0 [1]	3.0 (1.9) -moz	?	15 -webkit	6.1 -webkit^[2]
`border-box` and `content-box`	No support	No support	No support	No support	No support

Feature	Android	Android Webview	Firefox Mobile (Gecko)	IE Phone	Opera Mobile	Safari Mobile	Chrome for Android
Basic support	?	(Yes)	?	?	?	?	(Yes)
Animatability	?	?	16.0 (16.0)	?	?	?	?
`max-content`	?	46.0 [1]	?	?	?	?	46.0 [1]
`min-content`	?	46.0 [1]	?	?	?	?	46.0 [1]
`available`	?	?	?	?	?	?	?
`fill-available`	?	46.0 [1]	?	?	?	?	46.0 [1]
`fit-content`	?	46.0 [1]	?	?	?	?	46.0 [1]
`border-box` and `content-box`	?	?	?	?	?	?	?

[1] WebKit implements a variation of this value under the name fill-available as of December 2013.

[2] Earlier versions of WebKit implemented an earlier version of this value under the name intrinsic, but implements fit-content since version 6.1 as well.

[3] Unprefixed.

[4] Old WebKit support intrinsic and min-intrinsic keywords, but removed in Chrome 48.