How to Use the Dimension Tool in Illustrator

In this post, we are going to learn about a recent and underrated feature in Illustrator, the Dimension Tool! There was a time when we had to use the Pen Tool and text boxes to create visual guidelines in a design, but now we can do it in seconds, thanks to this incredible update!

In this step-by-step guide, I’ll show you how the Dimension tool can assist you in applying accurate size and angle measurements to objects in technical designs. We will also cover all three types of dimensions the tool supports and how you can customize your dimensions’ measurement units, line size, color, and text attributes.

The tips covered in this post are based on my Illustrator Advanced Course. When you become a BYOL member, you gain access to this course as well as my 30+ additional courses on After Effects, Photoshop,Illustrator, Lightroom, and more. As a BYOL member you will also enjoy personalized support, earn certificates, and tackle exciting community challenges. Head here to sign-up!

Let 's get started!

Dimension Tool and Dimension Types

I’ll start with a quick run through of the dimension types you can apply with the Dimension tool and add more detail as we tackle each one of them through this tutorial.

Where can we find the Dimension tool? In the Toolbar to the left of our workspace, of course! If you can’t locate the tool, click on the Edit Toolbar button (three dots), and drag it from the Modify section onto the toolbar. Once it’s set, click the Dimension tool to access the Dimension Types taskbar.

• Linear Dimensions measure straight distances between two points. We can use them to measure the length of a line segment, the width of a rectangle, or even the distance between two anchor points. This is best used for creating graphic design layouts and architectural or interior design plans.

• Angular Dimensions measure angles between lines or shapes. We can use them to measure the angle between two intersecting lines or an object’s rotation angle.This is best used for engineering drawings, isometric illustrations, or web design.

• Radial Dimensions measure the distance from the center to another point on a circle (radius) or the distance between two points on a circle (diameter).This is best used for creating circular objects, architectural plans, and pie chart designs.

Applying Linear Dimensions

Let’s start with Linear. As an example, I’ll use a tri-fold flyer mockup I’ve created to send to the printer. If you are signed up for the Illustrator Advanced Course, it is one of the resource files included for download.

We’ll measure one of flyer’s faces as a guide for the printer. Make sure the object is selected, click the Dimension Tool to open the Dimension Types taskbar. Next, pick the first option, Linear Dimension.

Next, we click the top line segment to measure and plot its width. Illustrator will instantly generate a dimension line displaying the width value.

If this looks a little hard to read, there is another way to do it. With both object and Linear type selected, click, hold, and drag the dimension line away from the line segment.

Illustrator will add extension lines to the dimension line for a clearer view.

Quick, easy, and accurate! One awesome detail: these are live measurements, so if you change the object’s width with the selection tool, the dimension line will automatically update to the new width value.

Applying Angular Dimensions

Now let’s have a look at angles and how we can measure them with the Dimension tool. We’ll practice with a shape I’ve created using the Pen Tool. Make sure the object is selected, click on the Dimension tool to open the Dimension Type taskbar, and pick the second option, Angular Dimension.

Hover the mouse cursor over the angle’s vertex until the guides appear and click to apply the measurement. In this example, we’ll find a 95-degree angle.

Another way to do it: Click and drag away from the vertex to measure the exterior angle and make the line more visible.

You can also drag inward from the vertex to measure the interior angle and display both dimension lines at the same time.

Applying Radial Dimensions

Last but not least, let’s move on to circles. We’ll use a basic ellipse shape, with Fill and Stroke colors, so you can easily understand how the tool works.

First, with the object selected, click on the Dimension tool to open the Dimensions Type taskbar, and click on the third option, Radial Dimension.

By default, Illustrator will start measuring from the circle’s center, so all we need to do is to click somewhere along the edge to find the radius value.

If we need to find the ellipse’s diameter, it’s just as easy. Click and hold a point along the edge and drag towards the center (just a bit, no need to drag all the way to the center point) and Illustrator will plot the diameter value. Done in no time! How cool is that?

Timeout #1

Want to know more about creating efficient layouts? I highly recommend this article. 

Editing Dimension Guides

Another cool feature we’ll cover is customizing Dimension guides. We can quickly edit both dimension and extension lines, as well as the generated text objects. Let’s push on and begin by updating dimension units!

If we select the linear dimension guide, we can find all the available editing options in the Properties panel:

• Dimension

• Dimension Line

• Extension Line

• Dimension Text

As we’ve seen before, our Linear dimension guide is presented in pixels. Why? It’s not a random thing, the Dimension tool uses the document’s dimension units by default. In this case, pixels.

Let’s say that our client or printer needs these dimensions set in millimeters. With the linear guide selected, we click on the Units drop-down box and select the requested measurement unit.

As simple as that! Our guides are now presented in millimeters and we can move on to further editing!

Next step, we need dimension and extension lines to have more contrast to make them easy to read. This is an easy task! If you select the Layers panel, you’ll see there’s a new independent layer in your document called Dimensions, just above the original artwork layer. This allows us to make all the changes we need to dimension guides without affecting any other elements in the document. Cool, right?

Let’s start with the dimension line. We can edit it from the Properties Panel, inside the Dimension Line. We click the Color swatch and choose a new color with the help of the Color Picker. It’s that simple! We can also change the line weight and type or customize the arrowhead to distinctive styles and scale size.

We can repeat these steps for the extension lines, using the Extension Line settings.

There is more! We can also customize our guide’s text elements. In the Dimension Text panel, we can adjust settings like Color, Font Family (also known as Typeface), Font Style and Size, Offset (the gap between dimension line and dimension text), and Position.

Timeout #2

Get inspired with this gallery of technical designs and create your own incredible solutions with the help of your new Dimension tool skills!

Expanding Dimension Guides

This can be really helpful as a final change. As we’ve seen so far, the Dimension tool is quite dynamic, measuring unit values (like pixels or millimeters), and automatically updating them when changes are made to an object.

But what if we need more than a basic value in pixels or millimeters? What if we need to add information or set a guideline for a specific measurement?

To change the value information, we need to Expand the dimension guide. We’ll release it from the Settings we’ve changed before and edit it as a common vector object. To do this, we can click on the Expand button at the lower level of the Properties panel or click Object in the top menu bar and then choose Expand Appearance.

We can now change the information to the detail we need, by editing its content and settings as any text object, from the Character panel.

Remember that all dimension links are broken, so the measurement value is no longer dynamic. If you change the object’s size, the dimension guide won’t update by itself, it will have to be changed manually.

And there we have it!

Allright, now we know how the Dimension tool can streamline our work and take our designs to a higher level of precision and professional presentation. We had a look at some basic examples, but I’m sure you can now imagine how these skills will be key to any technical design. I hope you’re already sketching new ideas to practice what you’ve learned and I’m genuinely happy to share the enthusiasm! Good luck!

What 's Next?

To go deeper with Illustrator, join BYOL and you will gain access to my Illustrator Essentials and Advanced courses as well as my 30+ additional courses on Figma, Photoshop,  Lightroom, Premiere Pro, Webflow, and more. As a BYOL member you will also enjoy personalized support, earn certificates, and tackle exciting community challenges. Get started here. 

See you in class! – Dan