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block-size

The block-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 block-size relates to the width of the element; otherwise, it relates to the height of the element. A related property is inline-size, which defines the other dimension of the element.

Try it

Syntax

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

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

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

/* Global values */
block-size: inherit;
block-size: initial;
block-size: revert;
block-size: revert-layer;
block-size: unset;

Values

The block-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 block-size of containing block
Computed value same as width and height
Animation type a length, percentage or calc();

Formal syntax

block-size = 
<'width'>

Examples

Block size with vertical text

HTML

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

CSS

.exampleText {
  writing-mode: vertical-rl;
  background-color: yellow;
  block-size: 200px;
}

Result

Specifications

Browser compatibility

Desktop Mobile
Chrome Edge Firefox Internet Explorer Opera Safari WebView Android Chrome Android Firefox for Android Opera Android Safari on IOS Samsung Internet
block-size 57 79 41 No 44 12.1 57 57 41 43 12.2 5.0
fit-content 57 79 41 No 44 12.1 57 57 41 43 12.2 5.0
fit-content_function No No 91 No No No No No No No No No
max-content 57 79 6641 No 44 12.1 57 57 6641 43 12.2 5.0
min-content 57 79 6641 No 44 12.1 57 57 6641 43 12.2 5.0

See also

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https://developer.mozilla.org/en-US/docs/Web/CSS/block-size