Aspect ratio calculator
Find the aspect ratio (e.g. 16:9) of an image or screen and resize keeping the proportion.
How the calculation works
The aspect ratio is width:height simplified by the GCD. To resize keeping the ratio: new height = new width × height ÷ width.
Examples
- 1920×1080 simplifies to 16:9; 1024×768 to 4:3.
- Keeping 16:9 at width 1280 → height = 1280 × 9 ÷ 16 = 720.
Frequently asked questions
What is the Full HD ratio?
1920×1080 is 16:9, the standard widescreen video ratio.
How to resize without distortion?
Keep the ratio: fix width or height and compute the other by the same ratio. Changing just one stretches the image.
What are the black bars on video?
They appear when the video ratio differs from the screen (e.g. a 21:9 film on a 16:9 TV). Called "letterboxing".
Aspect ratio versus resolution?
Aspect ratio is the shape (16:9, 1:1); resolution is the pixel count. 1280 × 720 and 1920 × 1080 are both 16:9.
How do I adapt an image to another ratio?
Crop it or add bars. Never stretch — the distortion is immediately visible.
Which ratios do social networks use?
9:16 for Stories and Reels, 1:1 for square posts, 4:5 for vertical feed and 16:9 for YouTube.
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Updated on June 18, 2026 · by Rafael Rossi · Methodology & sources