Aspect Ratio Calculator
Work out a missing width or height while keeping a fixed aspect ratio, or reduce any width and height down to its simplest ratio. Useful for video, screens, photos and responsive layouts.
How to use the aspect ratio calculator
- Pick a mode: Resize to find a missing dimension, or Simplify to reduce a size to its ratio.
- In Resize, type a ratio such as 16:9 and the one dimension you already know.
- Read the matching dimension or the simplified ratio, then copy the result.
Examples
Resize a 16:9 width to its height
Ratio 16:9, width 1920
height 1080
Simplify a 4:3 resolution
1024 x 768
4:3
Frequently asked questions
What is an aspect ratio?
An aspect ratio is the proportional relationship between width and height, written as two numbers like 16:9. It describes shape, not size, so 1280x720 and 1920x1080 share the same 16:9 ratio.
What are the most common aspect ratios?
16:9 is standard for video and most screens, 4:3 is older displays and many photos, 1:1 is square social posts, 21:9 is ultrawide and 9:16 is vertical phone video.
How do I resize an image without distorting it?
Keep the same ratio. Use Resize mode: enter the original ratio and your new width, and the tool gives the height that holds the proportions so nothing stretches.
How does the simplify mode work?
It divides the width and height by their greatest common divisor. For example 1920 and 1080 share a divisor of 120, which reduces to 16:9.
Where are aspect ratios used in photo and video?
Cameras shoot 3:2 or 4:3, films use 16:9 or wider, and social platforms expect 1:1, 4:5 or 9:16. Matching the target ratio avoids unwanted cropping or black bars.
Does this run in my browser?
Yes. All calculations happen locally in your browser, so nothing you type is uploaded or stored.
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