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
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 toauto. auto- The width depends on the values of other properties. The browser will calculate the width accordingly.
 stretch- 
    
Uses
stretch-fit inline sizeorstretch-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 
inheritorinitial, 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:
Official Specifications
- CSS basic box model (W3C Editor's Draft)
 - CSS Intrinsic & Extrinsic Sizing Module Level 3 (W3C Working Draft)
 - CSS Level 2.1 (W3C Recommendation 07 June 2011)
 - CSS Level 1 (W3C Recommendation 17 Dec 1996)