How to Change Units in Photoshop

For various jobs, you might need to use multiple measuring scales in Photoshop. For instance, some tasks might require you to work in millimeters or inches, while others would benefit from working in pixels.

Knowing how to change your measurement units in Photoshop is an important step to learn. Adobe Photoshop has seven different types of units. The types of units are as follows. 

  • Pixels
  • Inches
  • Centimeters
  • Millimeters
  • Points
  • Picas (1 pica = 12 points)
  • Percent

My name is Aly, and I am Adobe Photoshop certified. From my experience working with Photoshop over the years, I can tell you that you will need to change the file unit at some point since you will not always find that working in one unit of measurement is the best for certain projects you may have. 

In this tutorial, I will show you how to change the type of units to measure different projects in Adobe Photoshop. 

How to Change Units in Photoshop

Units are essential to the project you are working on because, without the right units, you may have issues figuring out the correct forms of measurement. 

Step 1: To begin, select Photoshop > Preferences from the menu at the top of the screen to set the preferred unit your projects will use by default. The Preferences pop-up window will then show up. Click Units & Rulers.

Step 2: After you have clicked on the Units & Rulers option, a box dialog will open and will look like the image below. You can decide which unit type best fits your project by clicking on the dropdown menu below the rulers and type options. 

For example, you can change px to mm in Photoshop. Once you’ve chosen your desired unit of measurement, click OK and your selection will be saved. Now you will be working in the selected unit. 

Please note that changing this parameter will not affect the actual canvas size of your project. Instead, it will only alter the tools’ unit of measurement and the units used to measure the size.

Which Measurement Unit Should You Use

You will be able to select the precise measurement unit to use based on your requirements, once you understand how to modify the measurement unit in Photoshop. 


A pixel, which is short for “picture element,” is a small component of your picture. Unless you zoom in or raise the image size, you probably won’t be able to see the individual pixels in your photo. In the first image below, there are no discernible pixels, and the complete image is visible. 

However, the zoomed version makes the individual pixels easy to observe.


But when working with photographs that need to be a certain size for printing or publication, measuring in inches might be helpful. In print, inches are frequently utilized.

Millimeters and Centimeters 

As with inches, artists who work in or create work for markets outside of the United States will find it useful to measure their photos in millimeters or centimeters. Using millimeters or centimeters, which are sometimes used to determine print proportions, can enable you to alter your photo precisely.

Picas and Points

To measure type, picas, and points are most commonly used. The common unit of measurement for the type was the pica. 

Points are now increasingly frequently used as the standard unit of measurement for fonts. You’ve probably used the point system to choose the font size before. There are 12 points in a Pica.

Final Thoughts

Knowing when to use each system of units in Photoshop is essential to creating a great project. Learning about units is usually the first thing you should take into account when learning Photoshop as a beginner. 

Any questions about changing units in Photoshop? Leave a comment and let me know.

About Aly Walters
As a graphic designer who uses the entire Adobe Suite on a daily basis, Photoshop is my inspiration, especially since I'm Adobe certified and use it most often for my graphics and web-designed images.

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