Image aspect ratio describes the relationship between width and height. It is the shape of a picture, not its file size or visual quality. Keeping the same ratio while resizing avoids accidental stretching.
Start with the shape you actually need
A landscape feature image often works well at 16:9, while a square card is 1:1. Portrait imagery might use 4:5 or 9:16 depending on the layout. These are planning ratios, not permanent requirements imposed by any particular platform. Check the destination's current specifications before publishing.
How to calculate a matching height
Suppose your original image measures 1920 × 1080 pixels. Divide both values by their greatest common divisor, 120, to get a 16:9 ratio. If the layout needs a 1280-pixel-wide copy, multiply 1280 by 1080/1920. The correct height is 720 pixels.
Resizing is not cropping
Resizing keeps the frame's shape; cropping changes what is visible. If the original and required shape differ, choose a deliberate crop rather than distorting the image. Keep people's faces, embedded text and key subjects inside the safe area, and inspect the result at mobile width.
Keep image downloads efficient
Export a source image near its actual displayed dimensions, compare WebP/JPEG/PNG output, and check sharpness and file size. Always provide meaningful alternative text where images carry information, and set width/height dimensions to reduce layout shift.
Calculate proportional image sizes → · Resize and export an image →