Google Image Search has an undocumented parameter that lets you specify the exact dimension of the image that lets you filter results by size, instead of searching for small, medium and large images “imagesize:WIDTHxHEIGHT”. The operator could be useful if you need to find wallpapers, logos, illustrations for a school project or any other images that have standard sizes. Here's an example: [imagesize:640x480 muffin] finds 640px x 480px images related to muffins.

Source:→ Google System