Once you are happy click command + K and that will crop the image.

Once you have the correct sized box un-click the mouse, and you’ll be able to move the box to prime position.

You will see a little counter in the bottom right corner that shows how many pixels are selected.

If you want the image to be a particular size, like 1,600 x 900 in the example above, you can drag the box to the dimensions you need.

Click on the image in Preview and drag so that the blue box surrounds the part of the image you want to crop.If you want to crop an image it’s not immediately obvious how to do so because there isn’t a traditional crop tool in the menu, but it’s actually very easy.

If you are trying to shrink the image to 500KB for example, you can keep adjusting until you are happy with the result here. (It may take a while to calculate the size.) If you open the Adjust Size menu as above you will notice that when you adjust the dimensions of the image you will see a preview of the size (in MB or KB) of the image before and after you have make your changes. If you are trying to make the size of the image smaller (perhaps so you can send it via email) there are a couple of ways you can do so. But what if it’s the size of the image – in terms of MB – you want to change? How to make an image smaller That will change the dimensions of the image, perhaps you need the width to be the same as the width of a webpage you are adding the image to, for example.

Adjust either the Width number or the Height number – the other will automatically adjust proportionally.

Choose whether you want to resize according to pixels, percent, inches, cm, mm or points.

This means you can only change one dimension, length or width, but it means everything will be adjusted equally.

Now, assuming want your image to look the same after – rather than stretched or squat, you need to make sure that Scale proportionally is selected.Choose Adjust Size (you can also open this menu by clicking on the square with arrows icon in the menu bar).Double click on the image – this should open the image in Preview, if it doesn’t, close it and right click to choose Open With and select Preview.

Locate the image (either using the Finder, or on your Desktop).

How to edit photos in preview