Some icon sizes are standard and easy to find tools for, but 28x28 is one of the smaller ones that app developers, browser extension builders, and certain CMS platforms rely on for fixed size thumbnails in their interface. It is specific enough that most general image editors make you do the math yourself or fight with aspect ratio locks to get there. Needing a 28x28 image converter that just takes the number and outputs the file is a reasonable thing to want.
How to Resize an image to 28x28 pixels
Put 28 in the width field and 28 in the height field. One important thing before hitting resize, turn the Maintain Aspect Ratio checkbox off. With it on, any image that is not already a perfect square will come out with one side shorter than 28. Turning it off forces both dimensions to exactly what you typed.
Simple icons and flat graphics translate well at this size. A detailed photo will lose a lot of its detail at 28 × 28 because the canvas is just too small to hold it. If you are working with a photo, cropping it down to the most important part before resizing gives a cleaner result.
Got a batch of images that all need to be this size? Drop them all in together. One ZIP comes out at the end with everything resized.
Common Uses for 28x28 Images
Browser extension icons use this size. Most extension stores require icons at multiple sizes and 28x28 is one of the standard ones in that set alongside 16x16 and 48x48. WordPress and certain other CMS platforms also generate thumbnail sizes in this range for admin panel previews and media library displays.
App developers working on older Android projects or building icon sets for toolbars and navigation elements also run into this size regularly. It is small, but it shows up enough that having a quick way to hit it exactly saves time.
Output Quality at This Size
At 28x28, there are only 784 pixels to work with in total. That sounds like a lot until you are looking at an actual image that size. A clean icon or logo scaled down from something large will look sharp. A photograph with fine detail will not, and no tool changes that.
PNG is the better format here. JPEGs at very small sizes tend to look softer around edges, and you also lose transparency, which matters when an icon needs to sit inside an interface without a background box showing around it.