block-size CSS property
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 block-size CSS property defines the size of an element's block along the block axis. If the writing-mode is horizontal, it corresponds to the height; if the writing mode is vertical, it corresponds to the width. A related property is inline-size, which defines the other dimension of the element.
Try it
block-size: 150px;
writing-mode: horizontal-tb;
block-size: 150px;
writing-mode: vertical-rl;
block-size: auto;
writing-mode: horizontal-tb;
block-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 block-size.
</div>
</section>
#example-element {
display: flex;
flex-direction: column;
background-color: #5b6dcd;
justify-content: center;
color: white;
}
Syntax
css
/* <length> values */
block-size: 300px;
block-size: 25em;
block-size: anchor-size(height);
block-size: calc(anchor-size(--my-anchor block) * 0.75);
/* <percentage> values */
block-size: 75%;
/* Keyword values */
block-size: max-content;
block-size: min-content;
block-size: fit-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'>
<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
Block size with vertical text
HTML
html
<p class="exampleText">Example text</p>
CSS
css
.exampleText {
writing-mode: vertical-rl;
background-color: yellow;
block-size: 200px;
}
Result
Specifications
| Specification |
|---|
| CSS Logical Properties and Values Module Level 1 # dimension-properties |
| CSS Box Sizing Module Level 4 # sizing-values |
Browser compatibility
| desktop | mobile | |||||||||||
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block-size
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anchor-size()
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auto
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fit-content
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fit-content()
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max-content
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min-content
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stretch
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Legend
Tip: you can click/tap on a cell for more information.
- Full support
- Full support
- No support
- No support
- Experimental. Expect behavior to change in the future.
- User must explicitly enable this feature.
- Uses a non-standard name
- Requires a vendor prefix or different name for use.
- Has more compatibility info.
See also
- The mapped physical properties:
widthandheight writing-mode