Aspect Ratio Calculator

About Aspect Ratio

Reduces width and height to their simplest ratio, and works out the missing dimension when you fix the other one. It is the arithmetic behind resizing an image without distorting it, and behind fitting a video into a container cleanly.

The common ratios are worth recognising on sight: 16:9 for video, 4:3 for older displays and many documents, 1:1 for social avatars and product tiles, 21:9 for ultrawide, and 1.91:1 for most link preview images.

Where it helps

• Simplifies any pair of dimensions to their lowest terms.
• Solves for the missing width or height at a target size.
• Prevents the stretching that comes from resizing one axis by hand.
• Instant, so it fits into an export or a layout decision.

Limits

• Results are often fractional; rounding to whole pixels shifts the ratio very slightly.
• Unusual dimensions reduce to ratios like 683:384, which are correct but not memorable.
• It does not crop — fitting a different ratio means choosing what to lose, which is an editorial decision.
• Device pixel ratio is a separate multiplier for high-density screens.

Frequently asked questions

How do I resize without distortion?

Fix one dimension and let this calculate the other. Changing both independently is what stretches an image.

What ratio should a social preview image be?

1.91:1 for Open Graph — 1200 by 630 is the standard size. Square works better for feed posts.

Why is my ratio something like 683:384?

The dimensions do not share a tidy common factor. It is accurate; adjust by a pixel or two if you want a recognisable ratio.

Can I use this for CSS aspect-ratio?

Yes — the simplified ratio drops straight into aspect-ratio: 16 / 9 and the browser handles the rest.

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