inline-size

Baseline Widely available *

This feature is well established and works across many devices and browser versions. It’s been available across browsers since ⁨January 2020⁩.

* Some parts of this feature may have varying levels of support.

The inline-size CSS property defines the size of an element's block along the inline axis. If the writing-mode is horizontal, it corresponds to the width; if the writing mode is vertical, it corresponds to the height. A related property is block-size, which defines the other dimension of the element.

Try it

inline-size: 150px;
writing-mode: horizontal-tb;

inline-size: 150px;
writing-mode: vertical-rl;

inline-size: auto;
writing-mode: horizontal-tb;

inline-size: auto;
writing-mode: vertical-lr;

<section class="default-example" id="default-example">
 <div class="transition-all" id="example-element">
 This is a box where you can change the inline-size.
 </div>
</section>

#example-element {
 display: flex;
 flex-direction: column;
 background-color: #5b6dcd;
 height: 80%;
 justify-content: center;
 color: white;
}

Syntax

css

/* <length> values */
inline-size: 300px;
inline-size: 25em;
inline-size: anchor-size(width);
inline-size: anchor-size(--my-anchor inline);
/* <percentage> values */
inline-size: 75%;
/* Keyword values */
inline-size: max-content;
inline-size: min-content;
inline-size: fit-content;
inline-size: fit-content(20em);
inline-size: auto;
/* Global values */
inline-size: inherit;
inline-size: initial;
inline-size: revert;
inline-size: revert-layer;
inline-size: unset;

Values

The inline-size property takes the same values as the width and height properties.

Formal definition

Initial value	`auto`
Applies to	same as `width` and `height`
Inherited	no
Percentages	inline-size of containing block
Computed value	same as `width` and `height`
Animation type	a length, percentage or calc();

Formal syntax

inline-size = 
 <'width'> 

<width> = 
 auto | 
 <length-percentage [0,∞]> | 
 min-content | 
 max-content | 
 fit-content( <length-percentage [0,∞]> ) | 
 <calc-size()> | 
 <anchor-size()> | 
 stretch | 
 fit-content | 
 contain 

<length-percentage> = 
 <length> | 
 <percentage> 

<calc-size()> = 
 calc-size( <calc-size-basis> , <calc-sum> ) 

<anchor-size()> = 
 anchor-size( [ <anchor-name> || <anchor-size> ] ? , <length-percentage>? ) 

<calc-size-basis> = 
 <size-keyword> | 
 <calc-size()> | 
 any | 
 <calc-sum> 

<calc-sum> = 
 <calc-product> [ [ '+' | '-' ] <calc-product> ] * 

<anchor-name> = 
 <dashed-ident> 

<anchor-size> = 
 width | 
 height | 
 block | 
 inline | 
 self-block | 
 self-inline 

<calc-product> = 
 <calc-value> [ [ '*' | / ] <calc-value> ] * 

<calc-value> = 
 <number> | 
 <dimension> | 
 <percentage> | 
 <calc-keyword> | 
 ( <calc-sum> ) 

<calc-keyword> = 
 e | 
 pi | 
 infinity | 
 -infinity | 
 NaN

Examples

Setting inline size in pixels

HTML

html

<p class="exampleText">Example text</p>

CSS

css

.exampleText {
 writing-mode: vertical-rl;
 background-color: yellow;
 inline-size: 110px;
}

Result

[フレーム]

Specifications

Specification
CSS Logical Properties and Values Level 1 # dimension-properties
CSS Box Sizing Module Level 4 # sizing-values

Browser compatibility

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This page was last modified on ⁨Aug 9, 2025⁩ by MDN contributors.

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