CSS width

The CSS width property is used to specify the width of an element.

More specifically, the width property sets the width of the content area or border area (depending on the value of the box-sizing property) of certain boxes.

You can use a length or percentage to specify the width, or you can use one of the keywords.

Also see the max-width, height, and max-height properties.

Syntax

width: [<length> | <percentage>] | available | min-content | max-content | fit-content | auto

Possible Values

length
Specifies a length value for the width (for example 300px). Negative values are illegal.
percentage
Specifies a percentage value for the width (for example 80%). This is calculated as a width of the generated box's containing block. Negative values are illegal.
available
Equal to the containing block width minus the current element's margin, border, and padding.
max-content
The max-content width.
min-content
The min-content width.
fit-content
Equal to max(min-content, min(max-content, available)).
fit-content(length-percentage)
If specified for the inline axis, uses min(max-content size, max(min-content size, length-percentage)); otherwise computes to auto.
auto
The width depends on the values of other properties. The browser will calculate the width accordingly.
stretch

Uses stretch-fit inline size or stretch-fit block size, as appropriate to the writing mode.

In addition, all CSS properties also accept the following CSS-wide keyword values as the sole component of their property value:

initial
Represents the value specified as the property's initial value.
inherit
Represents the computed value of the property on the element's parent.
unset
This value acts as either inherit or initial, depending on whether the property is inherited or not. In other words, it sets all properties to their parent value if they are inheritable or to their initial value if not inheritable.

General Information

Initial Value
auto
Applies To
All except for table rows, row groups, and non-replaced inline elements.
Inherited?
No
Media
Visual
Animatable
Yes (see example)

Example Code

Here are some examples of valid widths:

.box { 
  width: 75px 
  }
.box {
  width: 5vw;
}
.box {
  width: 80%;
}
.box {
  width: available;
}
.box {
  width: min-content;
}
.box {
  width: max-content;
}
.box {
  width: auto;
}

Official Specifications