Aspect ratio calculator

Scale any design to a target aspect ratio. Pick 16:9, 9:16, 4:3, 1:1, 21:9 or a custom ratio, set a base resolution, and get exact scaled dimensions plus copy-ready CSS.

How to Aspect ratio calculator

1. Step 1. Select a popular ratio preset or enter a custom width:height ratio.
2. Step 2. Type a base width or height — the matching dimension updates automatically.
3. Step 3. Apply a scale multiplier (0.25× – 4×) for exact target sizes.
4. Step 4. Copy the CSS aspect-ratio snippet into your project.

Frequently asked questions

How do I calculate the aspect ratio of an image?

Divide the width by the height and simplify. This tool does it instantly and gives you the reduced ratio plus scaled dimensions.

What is the best aspect ratio for YouTube?

16:9 for standard widescreen video, 9:16 for Shorts and mobile-first vertical content.

Does the aspect ratio stay the same when scaling?

Yes — every scaled size preserves the selected ratio exactly, so your design never distorts.