How to Compress Image Size in Laptop (Windows & Mac, in KB)

To compress image size in a laptop, the quickest route is a browser tool: open compress image, drag the photo in, choose a quality or an exact KB target, and download. It works the same on Windows, Mac, Chromebook and Linux, with no software to install, and the photo stays on your computer. If you prefer built-in apps, Windows Paint and Photos and Mac Preview can also shrink images, with less control over the final KB size.

Below are all four methods, and which one to use when.

Method 1: in the browser, with an exact KB size

This is the only method here that lets you type "100 KB" and get a file under 100 KB.

1. Open compress image in Chrome, Edge, Firefox or Safari.
2. Drag one or more photos onto the box, or click to choose them.
3. Set Compress by to Target size and type the limit, for example 100, with the unit on KB. Or open a preset such as compress image to 100 KB.
4. Download each file, or press Download all (.zip) if you added several.

The tool picks the highest JPG quality that fits the limit and reduces the dimensions only if it has to. Because it runs in your browser, the photos are not uploaded anywhere, which matters for ID photos and documents.

If you need specific dimensions too, use resize image. Type a width and height in pixels (or in cm, mm or inches with a DPI), and put your limit in the Max size (KB) box so it resizes and compresses in one go.

Method 2: Windows Paint resize

Paint is on every Windows laptop and can make a photo much smaller by reducing its pixel size.

1. Right-click the photo, choose Open with, then Paint.
2. On the Home tab, click Resize (shown as Resize and skew in Windows 11 Paint), or press Ctrl + W.
3. Choose Percentage or Pixels. Keep Maintain aspect ratio ticked so the photo does not stretch.
4. Enter a smaller size, for example 50% or a width of 1200 pixels, and click OK.
5. Go to File, Save as, JPEG picture, and save it under a new name.

Limits to know:

• Paint has no JPG quality slider and cannot aim for a KB number, so you check the size afterwards (right-click the file, Properties) and try again if it is too big.
• Saving a PNG as JPEG in Paint usually makes a photo much smaller, but any transparent areas will not survive.

Method 3: Windows Photos app

In Windows 11, the Photos app can resize an image. Open the photo, click the three-dot menu (See more) at the top, and choose Resize image. You can pick a preset size or define custom dimensions, and there is a quality setting for the saved copy. Save it as a new file so the original is kept.

Menus in Photos have changed between updates, so if you do not see the option, update the app from the Microsoft Store or use one of the other methods.

Method 4: Mac Preview

Preview on a Mac gives you a quality slider and shows the file size before you save, which makes it the best built-in option on either platform.

1. Open the photo in Preview.
2. To reduce dimensions, choose Tools, then Adjust Size. Pick pixels, keep Scale proportionally ticked and enter a smaller width.
3. Choose File, then Export.
4. Set Format to JPEG and drag the Quality slider left. The estimated File Size updates as you move it.
5. Click Save.

Preview still cannot aim for an exact KB number for you, but watching the file size while you move the slider gets you close. For PNGs, choosing JPEG in the export dialog is the biggest saving if you do not need transparency.

Which method should you use?

How to compress image size in KB, not just "smaller"

Built-in apps think in pixels, forms think in KB. The two are linked but not the same: KB depends on the pixel count, the format and the quality setting together. A 1200-pixel-wide JPG might be 150 KB at high quality or 60 KB at medium quality.

So if a form gives a KB limit:

1. Reduce the pixels to something reasonable for the use (a form photo rarely needs more than a few hundred pixels).
2. Then compress to the KB target with a tool that measures the file as it goes.

Our guide on resizing an image in KB explains the relationship between KB and pixels in more detail, and the image size and DPI guide covers cm and inch sizes.

Without software: privacy and speed

"Without software" usually means "I do not want to install something", not "I want to upload my passport photo to a stranger's server". Many online compressors do upload your file. Ours does not: the page loads once and the image is processed by your browser on your laptop. You can even disconnect from the internet after the page loads and it keeps working.

Common mistakes

• Overwriting the original in Paint. Use Save as with a new name.
• Checking size in the wrong place. On Windows, right-click the file and choose Properties; on a Mac, select it in Finder and press Cmd + I.
• Stretching the photo. Always keep the aspect ratio unless the form wants an exact shape; for that, crop first with crop image.
• Saving screenshots as PNG for upload. Photos are much smaller as JPG.

For phones, see the companion guide on how to compress image size in mobile.

Questions