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.

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: 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

<'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

Specification
CSS Logical Properties and Values Level 1 # dimension-properties

Browser compatibility

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