Dimensions are the essence of AutoCAD. In fact, they are the essence of any design program. They’re the reason the program was made, and the reason you are using it. So it’s important to know exactly how they work and how to use them

There are several aspect of dimensions that are worth looking at, including placing the dimension, dimension style, and tolerances. 

The first, most common type of dimension is the linear dimension. It measures a distance from one point to another, but it always measures along the x or y axis. To use it, click the top button on the dimension toolbar (or go to Dimension-> Linear), the click your first point. After you click you first point, click the second point, and move the cursor away from the part. The length of the extension will be the distance from the actual measurement to you third click.

The second type of dimension is the aligned dimension. You can find it on the dimension toolbar (second one don) or at Dimension-> Aligned. This dimension works the exact same way as the linear dimension, except that it measures “as the bird flies” from one point directly to the other.

The arc length dimension is third on the dimension toolbar. This is used to measure the actual length of an arc, like in a circle, and can also be found at Dimension->Arc Length. To use it, click on the arc segment that you want to measure, and drag it out the distance that you want to separate the part and the dimension. Done!

The radius dimension (fifth down on the toolbar, and at Dimension->Radius), is used by simply selecting the circle whose radius you want to measure, and then clicking where you want the dimension.

The diameter dimension works the same way, and is located seventh down on the toolbar, and at Dimension-> Diameter. Just click the circle or arc, and click where the dimension should be.

The last type of dimension is the angular dimension. This measured the angle between two lines. It’s located on the dimension toolbar, and at Dimension->Angular. Just click the first line, then the second, and then click where you want the dimension to be.

The dimension styles utility is an easy way to configure the way your dimensions look on your drawing. To open the dimension styles manager, go to Dimension->Dimension Styles, or click on the last button on the dimension toolbar.

From here, you can create new styles or edit the ones you already have. Once you are in the editing window, you have several tabs. You can edit almost anything about the dimensions in this area.

Some of the things you can edit include the color and lineweight (under the Lines tab), arrows (under the Symbols and Arrows tab), text (under the Text tab, believe it or not), and tolerances (under the Tolerances Tab). These settings can be very handy for adjusting the dimensions to look how you like them, and editing the tolerance settings.

Once you’ve adjusted the settings to your satisfaction, click OK. Make sure your style is selected, then click Set Current. This will apply to all new dimensions you create.

Congratulations! You now know how to create dimensions, and make them look like what you want.