FREE BROWSER TOOLContent creation
Aspect Ratio Calculator — Resize Image and Video Dimensions
Work out the shape and proportional dimensions of a thumbnail, generated image or video frame. Enter the original pixel dimensions and a new width; no image upload is required.
Calculations run in your browser. No account or API key is needed.
Your result
- Aspect ratio
- 16:9
- Proportional height
- 720 px
- Rounded dimensions
- 1,280 × 720 px
- Scale
- 66.67%
Aspect ratio: 16:9 Proportional height: 720 px Rounded dimensions: 1,280 × 720 px Scale: 66.67% CSS: aspect-ratio: 16 / 9;
How to use this tool
Enter the original width and height as positive whole pixels.
Choose the width you want for the resized asset.
Read the reduced ratio and calculated height, then use those dimensions in your editor.
Ratio and resolution answer different questions
The ratio describes a shape; resolution counts pixels. Both 1920 × 1080 and 1280 × 720 reduce to 16:9. The calculator divides the original dimensions by their greatest common divisor, then multiplies the new width by the original height-to-width fraction.
Rounding and cropping
An exact proportional height can be fractional. The result shows that value and the nearest whole-pixel size so you can decide how to export. Changing 16:9 artwork into a 9:16 frame requires cropping or adding space; merely scaling it cannot change the ratio. This tool calculates dimensions and does not resize an actual file.
Common questions
Can I use this for portrait artwork?
Yes. Enter the smaller dimension as width for a portrait image. A 1080 × 1920 frame reduces to 9:16.
What is the CSS output for?
It is an aspect-ratio declaration for a proportional layout box. Keep at least one dimension automatic for the property to affect its size.