Whether it's a 200×200 profile picture, a 600-pixel-wide blog image, or a passport photo at a specific size, resizing an image is one of the most common little tasks online. Here's how to do it properly.
Every image has an aspect ratio, the relationship between its width and height. A 4000×3000 photo has a 4:3 ratio. If you change the width and height in a way that doesn't match that ratio, the image gets stretched or squashed and looks wrong.
That's why the safe default is to keep the aspect ratio: you set one dimension (say width = 800) and the other is calculated automatically so the image stays perfectly proportioned.
Resizing already reduces the file size a lot. If you still need to hit a specific limit (like "under 100 KB"), run the result through the Compress tool afterwards.
Resizing changes how many pixels the whole picture has while keeping everything in view. Cropping cuts away the edges and keeps the original pixels of what remains. If a form wants a specific shape, crop to the right proportions first and then resize to the exact pixel size.
You changed the width and the height by different proportions. Keep the aspect ratio locked, then crop if the final shape must be different. A 4:3 photo forced into a square will always look distorted.
Not really. Enlarging only stretches the pixels that exist, so the result looks soft or blocky. If you need a larger version, go back to the original file, or use the image at its natural size and let the page scale it modestly.
Common sizes are 1080 x 1080 for square posts, 1080 x 1350 for portrait posts, 1080 x 1920 for stories and reels, and 1280 x 720 for video thumbnails. Platforms change these from time to time, so treat them as a starting point and check the current guidance before a big campaign.
On Windows, right click the file, choose Properties and open the Details tab. On a Mac, open it in Preview and use Tools then Show Inspector. On a phone, the Info or Details view in the gallery shows both dimensions and file size.