Aspect Ratio Calculator
Reduce any width and height to a clean aspect ratio, and resize to a target ratio by solving the missing width or height. Calculated in your browser.
Aspect ratio
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Show the math
The aspect ratio is width-to-height reduced by their greatest common divisor, 1920×1080 shares a divisor of 120, giving 16:9.
height = width × ratioH ÷ ratioW
Matching a platform's ratio avoids cropping or letterboxing. Everything is calculated in your browser.
What this does
An aspect ratio calculator reduces any width and height to a clean ratio, and resizes to a target ratio by solving the missing width or height.
How to use it
- Enter the width and height.
- Read the reduced ratio.
- Or enter a target ratio.
- Solve the missing dimension.
How it works
Dividing both sides by their greatest common divisor gives the simplest ratio — 1920×1080 shares 120, giving 16:9. To resize: height = width × ratioH ÷ ratioW.
ratio = (width : height) ÷ GCD
Understanding your result
The simplified ratio tells you the shape of an image independent of its size, useful for matching footage, planning a layout, or choosing a frame. When resizing to a target ratio, the tool keeps proportions so nothing stretches; if your source ratio differs from the target, you will need to crop or letterbox, since you cannot reach a new ratio by resizing alone without distortion.
Example
1280×720 reduces to 16:9; a 16:9 image 1000 px wide is 562 px tall.
Sources & methodology
Last updated .
Frequently asked questions
How is the aspect ratio found?
The width and height are divided by their greatest common divisor — 1920×1080 shares a divisor of 120, giving 16:9.
How do I resize to a ratio?
Enter a target ratio and one known dimension; the other is solved as height = width × ratioH ÷ ratioW (or the reverse), keeping the proportion exact.
Is anything uploaded?
No. Everything is calculated in your browser — nothing you enter leaves your device.
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