The inline-size CSS property defines the horizontal or vertical size of an element's block, depending on its writing mode. It corresponds to either the width or the height property, depending on the value of writing-mode.

If the writing mode is vertically oriented, the value of inline-size relates to the height of the element; otherwise, it relates to the width of the element. A related property is block-size, which defines the other dimension of the element.


/* <length> values */
inline-size: 300px;
inline-size: 25em;

/* <percentage> values */
inline-size: 75%;

/* Keyword values */
inline-size: max-content;
inline-size: min-content;
inline-size: fit-content(20em);
inline-size: auto;

/* Global values */
inline-size: inherit;
inline-size: initial;
inline-size: unset;


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

Formal definition

Initial valueauto
Applies tosame as width and height
Percentagesinline-size of containing block
Computed valuesame as width and height
Animation typea length, percentage or calc();

Formal syntax



Setting inline size in pixels


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


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



Specification Status Comment
CSS Logical Properties and Values Level 1
The definition of 'inline-size' in that specification.
Editor's Draft Initial definition

Browser compatibility

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See also