How to Set Units in AutoCAD: A Step-by-Step Guide

How to set units in AutoCAD? Getting your drawing units right in AutoCAD is one of the first steps you should take on any project. Whether you're working on an architectural floor plan, mechanical component, engineering drawing, or site plan, incorrect units can lead to serious problems with blocks, dimensions, and measurement scaling.

The good news is that if you're wondering "how to set units in AutoCAD", you're in the right place. AutoCAD has a units command that lets you control how distances and angles are expressed and interpreted within your drawings.

In this guide, we'll go over all the details of units in AutoCAD, including:

•    How drawing units work

•    How to configure units in AutoCAD

•    Which settings to pay special attention to

•    Common issues with drawing units

Why Are Units Important in AutoCAD?

Before you learn "how to set units in AutoCAD", understand that AutoCAD typically works in drawing units, not real-world units.

You can think of AutoCAD units like this:

•           1MM

•           1CM

•           1M

•           1"

•           1'

•           Or any other convention specific to the project

The application makes no assumptions beyond your project's conventions and the settings you choose.

So, if I draw a wall that's 5 units long, it could be 5 meters or 5 feet depending on the context of the drawing and the units settings.

That's why it's so important to set your drawing units at the beginning of the project.

AutoCAD: How to Set Units Using the UNITS Command

The most straightforward way to set AutoCAD units is to use the UNITS command.

Here's "how to set units in AutoCAD":

Step 1: Open the File

Open the DWG file you want to set the units for.

If you're starting a new project, it's best to set the units before creating any major elements.

Step 2: Launch the UNITS Command

Type the following in the command bar:

UNITS

And press Enter.

You should see the drawing units window.

It has a number of options that relate to the unit conventions and precision.

Step 3: Set the Length Type

Under the Length category, you'll see an option to set the Type.

The most common conventions are:

•           Decimal

•           Architectural

•           Engineering

•           Fractional

•           Scientific

The right choice depends on your discipline and personal preferences, but Decimal is preferred for engineering drawings and Architectural for architecturaldocumentation.

Step 4: Set the Precision

Precision dictates how many decimal places AutoCAD will show when using a particular unit type.

As you can see in the image above, we can choose from the following:

•           10

•           10.0

•           10.00

•           10.000

The higher the precision, the more accurate the engineering drawing will be. Architectural drawings usually require less precision.

Keep in mind that changing the precision won't affect the actual geometry in your drawing. It only affects how it looks.

Choosing the Right Drawing Unit Type

One of the most common questions when it comes to "how to set units in AutoCAD" is choosing the right display type.

Decimal units

Decimal units are great for engineering drawings and any other applications that require metric measurements.

They can be displayed in a variety of ways, but it's most common to see them in the following format:

125.50

Architectural units

Architectural units are most common in architectural drawings. They let you measure distances in feet and inches.

The numbers would typically look something like this:

8'-6"

Engineering units

Engineering units are similar to architectural units, but they use a different convention. The values look something like this:

5 1/2

Fractional units

Fractional units are similar to decimal units, but they're expressed in fractions rather than decimals. The values would look something like this:

5 1/2

AutoCAD: How to Set Units in Metric

If you're working on a metric project, "how to set units in AutoCAD" typically means picking a decimal unit type and setting a standard for what one unit equals in the real world.

For example, you might set a standard that one unit equals one millimeter or one meter.

The choice is entirely up to you, but it's important to pick the convention that makes the most sense for your project.

Setting millimeter (mm)-based units

Most mechanical and manufacturing drawings use millimeters.

For example, if I want to draw a 100 mm-long component, I can simply create a 100 mm-long line in AutoCAD if I'm using the mm convention.

Setting meter (m)-based units

Architectural and engineering drawings typically use meters.

If I wanted to create a drawing for a 10m-long wall, I could set the drawing to use meters and just create a 10m-long line in AutoCAD.

I would never mix these two conventions in the same drawing unless I have a specific reason to do so.

AutoCAD: How to Set Units in Imperial

The process for "how to set units in AutoCAD" in imperial is similar to setting metric units, except we have to decide whether we want to use inches or feet (or another convention) and adjust the display format.

Architectural drawings typically use feet and inches, while mechanical drawings typically use inches.

So, if you're working on an architectural drawing, it would make the most sense to set the units to use the Architectural convention. If you're working on a mechanical drawing, we'd use the Decimal display type and set the units to use inches.

Keep in mind that changing the display type won't actually change the geometry in your drawing. That's a very common mistake.

Understanding Insertion Units

Another "how to set units in AutoCAD" is the insertion scale.

These settings tell AutoCAD how to scale objects like blocks and drawings when they're inserted into another drawing.

For example, suppose I want to insert a block or drawing that was created using millimeters into an architectural sheet.

I need to make sure that the block or drawing scales properly when it's inserted.

This is where insertion units come into play.

Insertion units are important because they let AutoCAD know how to scale objects when they're transferred from one drawing to another.

So, if I have an engineering drawing that was built using millimeters and I want to insert it into an architectural drawing that was created using inches, AutoCAD will use the information in the insertion units to figure out how to scale the objects in the engineering drawing.

It's always a good idea to double-check your drawing units before inserting any blocks or drawings.

AutoCAD: How to Set Units and Measure Angles

In addition to setting units for length measurements, we also need to configure the units that AutoCAD will use for angles. To do this, go to the Angles group in the UNITS window.

You'll see a list of conventions to choose from.

•           Decimal degrees

•           Degrees/Minutes/Seconds

•           Gradians

•           Radians

•           Surveyor's units

The first option is the best place to start if you're working on a general CAD project. Surveyor's units are typically used in surveying and civil engineering applications. Any other units are largely obsolete or only used in very specific applications.

Setting the angle direction

In addition to setting the angle convention, you can also set the angle direction. These settings will dictate how AutoCAD measures and expresses angles.

Once again, the defaults are best for most applications. These settings only need to be changed in very specific cases, such as when you're working on a surveying project.

Double-Check the Units Before Copying or Pasting Objects

When working with multiple drawings, it's always a good idea to double-check the units before you copy and paste any geometry from one file to another.

For example, if I have a 100 mm-long line in one AutoCAD file and I copy and paste it into a file that uses a millimeter-to-inch convention, the line would measure 100 in instead of 100 mm.

That's why it's so important to make sure that the units in both files match.

If you find that the units in your files don't match, you may want to use a CAD standard to ensure that everyone who works with the files uses the same conventions.

AutoCAD: How to Set Units and Avoid Rescaling the Entire Drawing

One of the biggest misconceptions about "how to set units in AutoCAD" is that it resizes the entire drawing.

It does not.

Instead, the UNITS command controls how AutoCAD interprets and displays the drawing.

So, if I have a drawing that was created using the wrong convention (e.g., meters instead of millimeters), I'll have to go through a process to resize all the geometry.

Fortunately, we can do this using the SCALE command.

Let's say, for example, that I accidentally drew a 100 mm-long component using the 1:1 drafting convention in millimeters.

When I go to the drawing properties, it shows that the current units are set to millimeters.

If I go to the UNITS command and change the convention to inches, the drawing itself won't change.

All I've done is change how AutoCAD interprets the drawing, but the drawing itself is still 100 mm long.

If I want to change the 100 mm to 100 in, I would have to use the SCALE command.

How to Set Units in AutoCAD: Common Issues

There are a few drawing issues that typically arise when units are set incorrectly.

Objects are inserted at the wrong scale.

This happens when the insertion units don't match the drawing units. Double-check the units before inserting any blocks or drawings.

Dimensions show the wrong measurements.

Make sure that you've set the right units and that your dimensions are using the right conventions.

The drawing is too big or too small when you open it.

Sometimes the units are set incorrectly, which leads to drawings that are much bigger or smaller than intended.

Make sure that the drawing units match the conventions that you want to use.

Measurements don't look right.

Always use the measurement tools to get the most accurate measurements. Never rely on dimensions.

Using the Right AutoCAD Units Settings: Best Practices

When it comes to "how to set units in AutoCAD", there are a few best practices you should follow.

Set the units at the beginning of the project.

It's best to set the convention as early as possible rather than waiting until near the end of the project.

Always use a 1:1 scale when modeling.

The drawing units dictate the size of the geometry, so it's always best to use the 1:1 convention when modeling.

Never use arbitrary unit measurements.

Instead of randomly switching between mm, m, in, ft, and other units, pick the convention that you want to use and stick with it throughout the entire project.

Paying attention to insertion units

When inserting blocks or drawings, always make sure that the drawing units match the insertion units. Otherwise, the size of the geometry will be incorrect.

Using templates to speed things up

Consider using a template file or creating your own so that you can set the units and other important settings in advance.

Conclusion

Learning "how to set units in AutoCAD" is an important skill that will help you avoid many common issues with scaling and measurements. Using the UNITS command, you can control how AutoCAD interprets and displays the units, which is especially important when working with drawings or blocks from other files.

While there are several types of units, most drawings and blueprints use either millimeters, meters, inches, or feet.

Regardless of the convention you choose, the most important thing is to be consistent.

Before you start any project, make sure you're using the right drawing units.

Also, always use a consistent 1:1 scale when creating models.

Remember that changing the units doesn't resize objects.

If you need to resize objects, use the SCALE command.

Finally, always check the units in drawings that you receive or import from others. Following these best practices will eliminate many common problems with units in AutoCAD.

Frequently Asked Questions

What command sets units in AutoCAD?

The UNITS command lets you change the units for angles, lengths, precision, and insertion scale.

Does changing the units in AutoCAD resize the objects in the drawing?

No. Changing the units won't resize any objects. If there are objects that are too big or too small, you'll have to manually change the scale.

What units should I use for AutoCAD?

It depends on your needs, but metric units are typically easier to work with. Common units include mm, m, in, and ft.

How do I set AutoCAD to millimeters?

Use the UNITS command and set the unit display to Decimal.

How do I change AutoCAD to millimeters?

Use the UNITS command and set the units to millimeters.

Why are blocks being inserted at the wrong scale?

It's probably because the insertion units in the block's file don't match the units in the current file.