Aspect Ratio Calculator
Last updated: June 2026
Formula
Aspect ratio = width and height divided by their greatest common divisor. Scaling keeps width / height constant.
| Ratio | Common use |
|---|---|
| 16:9 | HD video, modern TVs |
| 4:3 | Old TV, iPad |
| 1:1 | Instagram square |
| 9:16 | Phone vertical video |
| 21:9 | Ultrawide |
| 3:2 | DSLR photos |
About this calculator
The Aspect Ratio Calculator helps you simplify image and video dimensions, scale media without distortion, and fit an image or video into a container. It is useful for YouTube thumbnails, social videos, websites, presentations, TV graphics, and design exports.
Aspect ratio formula
The calculator finds the greatest common divisor of width and height, then divides both dimensions by that number.
- aspect ratio = (width / gcd):(height / gcd)
- decimal ratio = width / height
- scaled height = new width / decimal ratio
How to use the aspect ratio calculator
- Choose whether to find a ratio, scale dimensions, or fit to a container.
- Enter the original width and height in pixels.
- For scaling, enter either the new width or new height.
- For fitting, enter the container width and height.
- Use the simplified ratio for labels and the scaled dimensions for exports.
Worked examples
Full HD video
Input: 1920 x 1080
Calculation: gcd(1920, 1080) = 120. 1920 / 120 = 16, 1080 / 120 = 9.
Result: Aspect ratio 16:9.
Scale a 16:9 image
Input: Original 1920 x 1080, new width 1280
Calculation: 1280 / (16/9) = 720.
Result: Scaled size 1280 x 720.
Common video ratios
16:9 is standard for HD video and modern TVs. 9:16 is vertical phone video. 1:1 is square. 21:9 is ultrawide. Keeping the correct ratio avoids stretching or squashing the image.
Fit vs fill
Fit keeps the whole image visible inside a container, which can leave empty space. Fill covers the container but may crop part of the image. This calculator focuses on fit dimensions.
Common aspect ratio mistakes
- Changing width and height independently, causing distortion.
- Confusing pixel dimensions with physical screen size.
- Cropping a video to fit a ratio without checking important subject placement.
Media export disclaimer
This calculator handles geometry only. Export quality also depends on codec, bitrate, colour profile, compression, and platform requirements.
Frequently asked questions
What is 1920 x 1080?
It is a 16:9 resolution, commonly called Full HD.
What is 1080 x 1920?
It is 9:16 vertical video, common for phone-first platforms.
Can I use this for images?
Yes. Aspect ratio works the same for images, video, slides, and canvases.
What does decimal ratio mean?
It is width divided by height. A 16:9 image has a decimal ratio of about 1.778.
Why use gcd?
The greatest common divisor reduces width and height to the simplest whole-number ratio.
Related calculators
- TV Dimensions Calculator
- Screen Resolution Calculator
- Ratio Calculator
What does this mean?
This calculator is designed to help you understand the likely number before you make a decision or start an application.
Your result should be checked against official UK guidance, especially if your circumstances include dependants, exemptions, prior leave, or a complex immigration history.
Treat the figure as a planning tool rather than legal advice. Where the answer affects an application deadline or major payment, speak to an authorised adviser.
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