How to Resize an Image

Resizing an image is one of the first photo-editing tasks beginners learn on the computer. You can use a number of different ways to resize images – Photoshop, MS Paint, dedicated web applications, mobile apps, etc. In this tutorial, we will learn how to resize an image using three of the most popular methods around. You will also learn about the differences between image resizing and resampling.

To learn more advanced photo-editing tricks, check out this course to master Photoshop fundamentals.

Three Image Resizing Methods

Below, we’ll take a look at three different methods for resizing images: using Photoshop, MS Paint and web applications. We’ll be using this image for all editing purposes:

Method 1: Using Photoshop

If you already own Photoshop, resizing an image will take just a few clicks (or keystrokes, for those of you who like their shortcuts). Follow the steps given below:

1. Go to File -> Open to open the image in Photoshop, or hit CTRL + O


2. Once the image is open, go to Image -> Image Size or press CTRL + ALT + I

3. In the dialog box that pops up, enter your dimensions in the ‘Pixel Dimensions’ field. The default measurement unit will be pixels, though you can change it to inches or centimeters as well.

Make sure to check ‘Constrain Proportions’. This ensures that the width is increased or decreased in proportion to the height and vice-versa.

Once you’re done, hit ok.

4. You’ll now see that the image size has changed. If you are happy with the results, just click File -> Save or CTRL + S to save the changes.

That was easy, right? But there are a few questions that need to be answered:

What is the Difference between ‘Pixel Dimensions’ and ‘Document Size’?

Changing the ‘Pixel Dimensions’ and ‘Document Size’ are the two options you have in the Image Resize dialog box.

  • Pixel Dimensions: This refers to the image size as measured in pixels. This shows how big or small the image will show up on the web or any other digital medium.

  • Document Size: This refers to the image size as it would appear in print. Hence, it is usually measured in inches.

Changing the pixel dimensions and document size isn’t exactly the same thing. The former is used to control the image size for digital mediums, the latter for print.

What is ‘Resample Image’?

Images can be resized or they can be resampled. This opens up a whole new Pandora’s Box of technical questions which are beyond the scope of this tutorial. For now, all that you need to know about resizing vs. resampling is that resizing simply refers to changing the dimensions of an image without altering the pixel count.

Resampling on the other hand, changes the pixel count of the image as well.

Consider an example: suppose you have a large sandwich that you want to distribute among your friends. You want everyone to get one bite of the sandwich. If you were to resize the sandwich, you would simply take a knife, chop up the sandwich into smaller pieces and serve it to your friends.

If you were to resample the sandwich, however, you would bake all new, bite-sized bread, and add shrunken, bite-sized lettuce, tomatoes, ham and cheese to it before serving it to your friend. In other words, you would create a miniature version of the bigger sandwich instead of cutting it up into smaller parts.

Resizing is quick and dirty and results in poorer image quality. Resampling is more advanced and follows a computer algorithm for better quality and image size. You can select from different resampling processes in the dropdown menu next to ‘Resample Image’. For a full overview of these different resampling methods, check out this article from CodingHorror.

For more information on how to use Photoshop effectively, take this course.

Method 2: Resizing Image with Microsoft Paint

If you don’t have Photoshop, you can turn to the humble MS Paint to resize images. This is a pretty painless process as described below:

1. Open the Image by pressing CTRL + O or going to ‘Open’ from the main menu.

2. After the image opens, hit CTRL + W or click on the ‘Resize’ link in the top menu bar to open the resize image dialog box.

3. Enter the desired pixel size or percentage. Make sure to check ‘Maintain aspect ratio’. This does the same job as ‘Constrain Proportions’ in the Photoshop image resize dialog box, i.e. it ensures that height/width are increased/decreased proportionately.

Resizing the image by to 50% of its original size turns it from this:

Into this:

4. After you’re satisfied with the new size, hit CTRL + S to save changes.

Using Apple’s iPhoto? Check out this course to master iPhoto for beginners!

Method 3: Using a Free Web Application

There are dozens of free web applications for resizing images. We’ll take one of the more popular ones – – for this example.

1. Go to and load your image by clicking ‘Browse’.

2. Once the image is loaded, click ‘Continue’ to bring up the image resize, crop and special effects menu.

3. On the next screen, you will see a bunch of options to manipulate your image. This includes:

  • Cropping.

  • Rotating and flipping image.

  • Special effects, including frame border, oil paint, rounded corners, etc.

  • Resizing image

In the ‘Resizing Your Picture’ section, choose ‘Custom Size’ and enter your desired dimensions:

Choose your desired output format in the ‘Save As’ section below. You can also select the quality of the output image (better = bigger file size).

Click “I’m Done, Resize My Picture!” when you’re finished.

You’ll now be taken to a new screen where you can save the resized image to your computer, get a direct link to use it on the internet, edit it again, or view it in your browser.

There are several other methods of resizing your image, all of which basically follow the same process as described above. You can resize images in iPhoto (Mac), GIMP (Linux) or use tools like Google Picasa. There are also dedicated apps on both iOS and Android that will help you resize images with a few taps.

Now that you know how to resize an image, you are ready to learn more advanced photo-editing and manipulation tricks. Consider taking this course to learn how to make your images pop.