How to use Aspect Ratio Calculator
The aspect ratio calculator simplifies a width and height into a clean ratio like 16:9 and scales it to a new size without distortion. Enter your original dimensions to see the simplified ratio, then type a new width to get the height that keeps the exact same proportions. It divides both numbers by their greatest common divisor to reduce the ratio, and multiplies through to resize. Everything runs in your browser, making it handy for images, video, screens, and print layouts where keeping proportions right matters.
- Enter the original width and height.
- Read the simplified aspect ratio.
- Enter a new target width.
- Read the height that keeps the ratio.
Your data never leaves your device — 100% private processing.
Common aspect ratios
A handful of ratios dominate screens and media. 16:9 is the standard for modern displays, video, and streaming. 4:3 is the classic ratio of older TVs and many photos. 3:2 is common in DSLR photography, 1:1 is the square used across social media, and 21:9 is ultrawide. Knowing the ratio of your source helps you crop and resize without unpleasant surprises: fitting a 16:9 video into a 4:3 space, for example, either leaves letterbox bars or crops the sides. This calculator names the ratio for you so you can match assets to the space they need to fill.
| Ratio | Use | Example size |
|---|---|---|
| 16:9 | Video, displays | 1920×1080 |
| 4:3 | Legacy screens | 1024×768 |
| 1:1 | Social squares | 1080×1080 |
Why proportional resizing matters
When you change only one dimension of an image or video, the result looks stretched or squashed because the ratio no longer matches the original. Proportional resizing avoids this by changing width and height together in lockstep. If you halve the width, you must halve the height; if you scale the width to 1280 from a 16:9 source, the height must be 720. This calculator does that arithmetic for you, so exported assets stay crisp and correctly shaped. It is especially useful when a platform demands a specific width but you still need the height to preserve the original look.
Worked examples
HD
Inputs: 1920 × 1080
Result: 16:9
Scale down
Inputs: 16:9 · new width 1280
Result: 1280 × 720
Legacy
Inputs: 1024 × 768
Result: 4:3
Glossary
- Aspect ratio
- The proportional relationship between an image or screen’s width and height.
- Greatest common divisor
- The largest number that divides both width and height, used to reduce the ratio.
- Letterboxing
- Blank bars added when content of one ratio is fitted into a different ratio.
- Resolution
- The pixel dimensions of an image or screen, such as 1920×1080.
Related reading
Frequently Asked Questions
Why use Aspect Ratio Calculator?
- Simplifies any width × height into its smallest whole-number ratio
- Scales to a new size while preserving proportions
- Recognizes common ratios like 16:9, 4:3, and 5:4
- Runs instantly in your browser with nothing uploaded
Common use cases
- Resize an image without stretching or squashing it
- Find the height for a target width at a fixed ratio
- Identify the aspect ratio of a screen or video
- Plan layouts and thumbnails that must match a ratio
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