auto

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
Animation type	a length, percentage or calc();
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: 25em border-box;
width: 75% 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.

fill

Use the fill-available inline size or fill-available block size, as appropriate to the writing mode.

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
CSS Intrinsic & Extrinsic Sizing Module Level 3 The definition of 'width' in that specification.	Working Draft	Adds new sizing keywords for width and height.

Browser compatibility

[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.

See also

• box model, height, box-sizing, min-width, max-width