Placeholder Image Size Calculator

This tool generates a placeholder image of any size you specify, along with its aspect ratio, megapixel count and a ready-to-use URL, for use while designing and building web pages. When laying out a website or app before the real images are ready, designers and developers use placeholder images, plain coloured rectangles of the right dimensions, to fill the space and check the layout. Working out the aspect ratio of a given width and height, and producing a placeholder of exactly those dimensions, is a small but frequent task. This tool handles it. You enter the width and height in pixels, and the calculator shows a live preview of a placeholder image at that size, the simplified aspect ratio, the total megapixels, and a placeholder image URL you can copy straight into your markup. The results update as you type, so you can experiment with dimensions and immediately see the shape. Use it to mock up image areas while designing, to check how a given size looks, to find the aspect ratio of a planned image, or to grab a placeholder URL for a prototype. The aspect ratio is the width to height in lowest terms, found by dividing both by their greatest common divisor, so 1920 by 1080 simplifies to the familiar 16 by 9. The megapixel figure, width times height divided by a million, gives a sense of the image's resolution. The placeholder URL points at a public placeholder service that returns a grey image of the requested dimensions, ideal for prototypes, though you would replace it with real images for production. Seeing the preview, ratio and URL together makes it quick to plan image areas and keep your layouts consistent.

Aspect ratio is width:height in lowest terms. Megapixels = width x height / 1,000,000. The URL uses a public placeholder service; replace with real images for production.