The aspect-ratio property in CSS defines the proportional relationship between an element’s width and height, ensuring consistent dimensions during resizing. 1. It allows elements to maintain a fixed ratio, such as 16/9 or 1/1, regardless of viewport changes. 2. It eliminates the need for older hacks like padding-based workarounds. 3. Common uses include responsive images, videos, cards, iframes, and grid layouts. 4. It can be combined with Flexbox, Grid, and object-fit for better control. 5. The browser calculates width or height automatically if one is set. 6. It is not supported in older browsers like IE, so compatibility should be checked. 7. When applied to image containers, it preserves proportions while allowing full coverage with object-fit: cover. The aspect-ratio property provides a clean and predictable solution for maintaining element shapes in responsive design.
The aspect-ratio
in CSS is a property that lets you define the proportional relationship between an element’s width and height. It tells the browser how wide the element should be relative to its height (or vice versa), which helps maintain consistent dimensions when the element resizes — especially useful in responsive design.

For example, if you set aspect-ratio: 16 / 9;
, the element will always keep a 16:9 ratio — like a widescreen video — no matter how the viewport changes.
Why aspect-ratio matters
Before this property existed, developers had to use hacky workarounds (like padding tricks) to preserve aspect ratios. Now, aspect-ratio
makes it simple and clean.

Common use cases:
- Responsive images and videos
- Maintaining card or container proportions
- Embedding iframes or iframes-like layouts
- Designing grids where items should keep a fixed shape
How to use it
You can set aspect-ratio
with a simple ratio:

.container { aspect-ratio: 16 / 9; }
Or for a square:
.square { aspect-ratio: 1 / 1; }
You can also use it with other layout tools like Flexbox or Grid:
.grid-item { aspect-ratio: 4 / 3; width: 100%; }
Now, even if the container changes size, the item keeps its 4:3 shape.
A few key details
- If you set a height, the width will be calculated based on the ratio (and vice versa).
- It works well with
object-fit
for images and videos. - Older browsers don’t support it (mainly IE and some older mobile browsers), so check compatibility if supporting legacy users.
Example with an image:
.video-wrapper { width: 100%; aspect-ratio: 16 / 9; overflow: hidden; } .video-wrapper img { width: 100%; height: 100%; object-fit: cover; }
This ensures the image fills the container without stretching, while keeping the correct proportions.
Basically, aspect-ratio
is a small property that solves a common layout problem in a clean, predictable way.
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