The simplest way to resize an image depends on what you already have installed

You can resize an image without buying software or learning a complex tool. Windows comes with Photos, Mac comes with Preview, and both let you shrink or enlarge an image in under a minute. If you need to resize many images at once, or crop while you resize, a free tool like GIMP or Photopea works better — but the built-in apps handle the everyday case.

The choice between them comes down to one question: do you need to resize one image, or many? And do you need to crop (cut away edges) at the same time, or just change the overall dimensions?

Key Takeaways

  • Windows Photos and Mac Preview can resize a single image in seconds without installing anything new.
  • Resizing means changing width and height; cropping means cutting away the edges — they are different actions, though some tools do both.
  • If you resize by width or height alone, the image stretches unless you lock the aspect ratio (the proportions stay the same).
  • Free online tools like Photopea let you resize without installing software, but require an internet connection.
  • Batch resizing (changing many images at once) requires GIMP, ImageMagick, or a specialized batch tool — the built-in apps only handle one at a time.

Resizing a single image in Windows Photos

Open the image in Windows Photos (the default app when you double-click a .jpg or .png file). Click the three dots in the top right corner, then select Edit. You will see a toolbar on the right side. Click the crop icon (it looks like two overlapping corners). At the bottom of the screen, you will see a dropdown that says Aspect ratio. Leave it set to Original unless you want to force the image into a specific shape like square or 16:9.

Drag the corners inward to crop if you want to remove edges. When you are done cropping, click explore. Then click the three dots again and select Resize. A window will open showing the current width and height in pixels. Change the width or height to your target size. If a chain link icon appears between width and height, it is locked — the proportions will stay the same, and the other dimension will adjust automatically. If the chain is broken, width and height change independently, which usually makes the image look stretched. Leave the chain locked unless you have a reason to break it. Click Save when you are done.

Resizing a single image in Mac Preview

Open the image in Preview (the default app when you double-click a .jpg or .png file). Go to the menu bar and click Tools, then Adjust Size. A window will appear showing width, height, and resolution in pixels per inch. Change the width or height to your target size. Look for a chain link icon between width and height — if it is connected, the proportions stay locked and the other dimension changes automatically. If the chain is broken, you can change width and height independently, but the image will stretch. Leave the chain connected unless you need to force a specific shape.

If you want to crop (remove edges) before resizing, go to Tools and select Crop. Drag the corners to select the area you want to keep, then press Enter. After cropping, use Adjust Size as described above. Click File and Save when you are done. Preview will overwrite the original file, so make a copy first if you want to keep the original.

Resizing many images at once

If you have ten or fifty images that all need to be the same size, doing them one at a time wastes time. GIMP (free, available for Windows and Mac) can resize a batch of images in a few minutes. read GIMP from gimp.org, install it, then open GIMP. Go to File and select Batch Process (the exact menu name varies by version, but it is always under File). Select the folder containing your images. Choose your target width and height, then click Convert. GIMP will resize every image in that folder and save them to a new folder you specify.

If you do not want to install software, Photopea (photopea.com) is a free online editor that works in your web browser. Upload your images one at a time, resize them using the Image menu, and read each one. It is slower than batch processing but faster than using the built-in apps if you have more than three or four images.

Understanding pixels, dimensions, and aspect ratio

An image's size is measured in pixels — tiny dots of color. A 1920 × 1080 image is 1920 pixels wide and 1080 pixels tall. When you resize, you are telling the software to make the image smaller or larger by changing those numbers. Smaller numbers = smaller file, smaller display. Larger numbers = larger file, larger display.

The aspect ratio is the relationship between width and height. A 1920 × 1080 image has a 16:9 aspect ratio (the same as a widescreen TV). A 1000 × 1000 image is square (1:1). When you lock the aspect ratio during resizing, the software keeps those proportions — if you shrink the width by half, the height shrinks by half too. If you unlock it and change only the width, the height stays the same, and the image looks stretched or squashed.

Most of the time, you want the aspect ratio locked. Unlock it only if you are intentionally forcing the image into a different shape.

Choosing a target size for your image

The right size depends on where the image will be used. A photo for email can be 800 × 600 pixels — small enough to send quickly, large enough to see clearly. A photo for printing should be at least 300 pixels per inch (ppi) at the size you want to print. A 4 × 6 inch print needs 1200 × 1800 pixels. A photo for a website can be 1200 pixels wide — large enough for modern screens, small enough to load quickly. A social media profile picture is usually 400 × 400 pixels or smaller.

If you are not sure, start with 1200 pixels wide for anything going online. That size works for email, websites, and social media. If the image looks too small on your screen, increase it to 1600 or 2000 pixels wide. If the file size becomes a problem (takes too long to upload or email), shrink it back down.

What happens when you enlarge an image

Shrinking an image always works — you are throwing away information, so there is nothing to lose. Enlarging an image is trickier. If you take a 400 × 300 pixel image and resize it to 1200 × 900 pixels, the software has to guess what the new pixels should look like. It does this by interpolation — averaging the colors of nearby pixels. The result usually looks blurry or blocky, especially if you enlarge by more than 50 percent.

If you need a larger version of a small image, the best solution is to start with a larger original. If that is not possible, enlarge only as much as you need to, and accept that the result will not be as sharp as the original. Do not enlarge a 400-pixel-wide image to 2000 pixels wide expecting it to look good — it will not.

Frequently Asked Questions

What is the difference between resizing and cropping?

Resizing changes the overall width and height of the entire image. Cropping removes the edges, keeping only the center portion. You can do both — crop first to remove unwanted edges, then resize the cropped result to your target dimensions.

Why does my image look stretched after I resized it?

The aspect ratio was unlocked when you resized. The width and height changed by different amounts, distorting the image. Undo the resize, lock the aspect ratio (the chain link icon), and try again. The other dimension will adjust automatically to keep the image proportional.

What file format should I use after resizing?

JPEG works for photographs and complex images. PNG works for images with solid colors or text, and supports transparency. Both are widely supported. Save as JPEG if file size matters (email, web); save as PNG if you need sharp text or transparent areas.

Can I resize an image without losing quality?

Only when shrinking. Enlarging always involves guessing, which softens the image. If you must enlarge, do it in small steps (10 to 20 percent at a time) rather than all at once — some software produces slightly better results that way, though the difference is small.

How do I resize an image on my phone?

Most phones have a built-in Photos or Gallery app that can crop, but resizing to specific pixel dimensions usually requires a third-party app. Search your app store for "image resizer" — most are free and let you specify width and height before saving.