If you need to reduce the size of an image (or images) because they are too large to email, to use online, or for another reason, you lot may be thinking that you need an expensive app such equally Photoshop, but you can easily resize images on a Mac using Preview, which comes complimentary with macOS.

Hither's how to resize images on Mac, including how to resize images without losing quality, resize images without stretching or distorting, how to resize images to same top and width and more.

Kickoff we'll look at the basics...

How to resize an paradigm using Preview

Here's what y'all need to do to change the dimensions of an image using Preview.

  1. Locate the paradigm (either using the Finder, or on your Desktop).
  2. Double click on the image - this should open the image in Preview, if it doesn't, close it and right click to choose Open up With and select Preview.
  3. Click on Tools.
  4. Cull Adjust Size (yous can also open this carte du jour by clicking on the square with arrows icon in the menu bar). Adjust Size Preview
  5. Now, bold desire your epitome to look the same after - rather than stretched or squat, you demand to make sure that Scale proportionally is selected. This means y'all tin merely modify one dimension, length or width, only it ways everything will exist adjusted equally. Change dimensions image Mac
  6. Choose whether you want to resize according to pixels, pct, inches, cm, mm or points.
  7. Conform either the Width number or the Height number - the other will automatically suit proportionally.

That will change the dimensions of the epitome, perhaps y'all need the width to be the same every bit the width of a webpage you are adding the prototype to, for instance. But what if information technology's the size of the prototype - in terms of MB - you want to change?

How to brand an image smaller

If y'all are trying to make the size of the paradigm smaller (perhaps then you lot can ship it via email) at that place are a couple of ways y'all can exercise so.

If you open the Suit Size menu as in a higher place yous will discover that when you adjust the dimensions of the image you will see a preview of the size (in MB or KB) of the paradigm before and later on y'all take make your changes. (Information technology may take a while to summate the size.)

If you lot are trying to shrink the image to 500KB for example, you can go along adjusting until yous are happy with the result here.

Another way to adjust the size of the image is via the quality settings in the Consign card.

  1. Click on File > Consign.
  2. Y'all will see various file formats to cull from. HEIC (the new file format), JPEG, JPEG-2000, OpenEXR, PDR, PNG or TIFF. Below the list is a measurement of file size. If you click through the unlike file options yous can see the file size change. JPEG is smaller than PNG, TIFF is bigger than PNG, for example. You could just select JPEG to get a smaller file size. Format choices
  3. Even having selected JPEG you tin can go a step further to reduce the file size past sliding the Quality bar from All-time to Least. Just adjust it until you get to a size that suits you. But retrieve that some of the quality will be lost.
  4. When yous are happy click on Relieve.Size of Jpeg

How to adjust an epitome, just maintain 300dpi

Speaking of quality… Y'all may as well want to get the best upshot possible at 300dpi (usually recommended for print), or some other resolution. In that example, hither's what to do:

  1. Deselect Resample epitome (scale proportionally will remain selected only greyed out.)
  2. In the section where it says resolution pixels/inch change the number to 300 (or whatever dpi is requested). 300dpi image Preview
  3. You will notice that the width and summit measurements will adjust, click OK.
  4. This won't adjust the actual size of the file, but it means that if the image was printed it would be smaller, but clearer, thanks to more than meaty pixels.

Resizing to particular dimensions

What if you desire to resize both the height and width of your image to particular dimensions, such as ane,600 x 900?

In Preview the all-time way to practise this is to use the crop tool. We'll expect at how to do that side by side.

How to ingather an image in Preview

If you lot want to crop an image information technology's not immediately obvious how to practise so because there isn't a traditional ingather tool in the menu, merely information technology'due south really very easy.

  1. Click on the image in Preview and drag so that the blueish box surrounds the part of the image you lot want to crop.
  2. If you lot want the image to be a particular size, like one,600 x 900 in the instance higher up, yous tin can elevate the box to the dimensions y'all demand. You will see a trivial counter in the bottom right corner that shows how many pixels are selected. Crop in Preview
  3. One time you have the correct sized box un-click the mouse, and yous'll be able to move the box to prime number position.
  4. Once you are happy click control + Chiliad and that will crop the image.

Resize without losing quality

You can't add together pixels to an paradigm then the merely way to make an image larger without losing quality (which is adamant by the number of pixels in a square inch) is to crop the image following the instructions in a higher place.

However you could cull HEIC, which is a space saving file type (it stands for High Efficiency Image Format) that should create an image that is smaller than a JPEG, but with the same quality.

HEIC files are half the size of a JPEG but offer the same quality.

HEIC in Preview

You can merely open up a HEIC file on a Mac with High Sierra or Mojave installed, or on iPhones and iPads running iOS 11 or iOS 12.

We accept an commodity about opening HEIC files on our sister site Tech Advisor. The advice is to employ a third political party app, such as such every bit iMazing HEIC Converter or Apowersoft'south HEIC to JPG converter, or an online converter such every bit HEIC to JPG.

How to batch resize

You tin also batch resize if at that place are a number of images yous desire to conform in one go. To practice then:

  1. Select all the images y'all want to resize by clicking on each one in the Finder, or on your Desktop, while pressing the Control key.
  2. Right click and choose Open with Preview.
  3. All the images will open in Preview. Select all by pressing Command + A (or choose Edit > Select All).
  4. Now go to Tools > Adapt Size (as we did before).
  5. If you are only adjusting width or height don't forget to select Calibration Proportionally.
  6. Yous will meet Multiple Values appear every bit the measurement in the columns (assuming all the images are dissimilar sizes). If yous want them all to be 1000 pixels wide, type 1000 in the Width box. Batch resize Mac
  7. Click OK to adapt the size of the selected images.
  8. Now printing Command + S to save (or File > Save) and all your images will be saved with the new dimensions.

How to change the file format

Speaking of saving what if you want to change the file format of the image. Nosotros touched on this earlier when we discussed reducing the file size as some file formats are smaller than others.

  1. To modify the file format click on File in the menu.
  2. Click Export…
  3. From the Format dropdown many choose either HEIC (the new file format), JPEG, JPEG-2000, OpenEXR, PDR, PNG or TIFF.
  4. With some of these options yous tin can too adjust quality (and therefore size). e.g. if you select JPEG yous will see a quality slider and it will show you the file size so you lot can adjust it downwards to a size that suits you lot.Format for image
  5. When you are happy click on Save.

We have more tips for using Preview on the Mac here. We also have information nigh how you can apply Preview to sign a PDF on a Mac and how to edit PDFs on a Mac.