Your monitor’s resolution is described in pixel dimensions. For example, if your monitor resolution and your photo’s pixel dimensions are the same size, the photo will fill the screen when viewed at 100%. How large an image appears on‑screen depends on a combination of factors—the pixel dimensions of the image, the monitor size, and the monitor resolution setting. In Photoshop, you can change the image magnification on‑screen, so you can easily work with images of any pixel dimensions.

A 620‑ by 400‑pixel image displayed on monitors of various sizes and resolutions.

When preparing images for viewing on‑screen, you should consider the lowest monitor resolution that your photo is likely to be viewed on.