Aspect Ratio Calculator
Enter width and height to get the simplified aspect ratio (16:9, 4:3 and more) and resize one side keeping perfect proportions. Instant and free.
Why aspect ratios matter
Every image, video and layout has an aspect ratio — the proportion between width and height. Change one side without the other and the content stretches or crops. This calculator simplifies any pair of dimensions to a clean ratio, lets you pick common presets, and computes the matching side when you resize.
What it does
- Simplifies any width and height to the smallest whole-number ratio.
- One-click presets: 16:9, 21:9, 4:3, 3:2, 1:1, 9:16.
- Resizing solver: enter a new width or height and get the matching side.
How to use
- Enter the original width and height, or click a preset.
- Read the simplified ratio and its decimal value.
- Enter a new width or height to compute the other side proportionally.
How it works
The ratio is simplified with the Euclidean algorithm (greatest common divisor), and the resize solver multiplies the ratio factors by your new side. All math runs locally in your browser.
Frequently asked questions
Why does 1920×1080 simplify to 16:9?
Both numbers are divided by their greatest common divisor — 120 in this case — leaving the smallest whole numbers with the same proportion: 16 and 9.
Can I use it for non-pixel dimensions?
Yes. Any consistent units work — centimetres, inches or abstract units — as long as width and height use the same one.
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