Optimizing CAD File Sizes: The Ultimate Guide

Typical CAD files used for architectural drawings and 3D parts and assembly drawings and models can be anywhere between a few kilobytes and a few gigabytes. Files that are one or two gigabytes in size are fairly common, but they can be problematic for some users. This is particularly true if their computers lack the capacity to handle large files or if the file size is unnecessarily inflated. In this article, we delve into the causes of large CAD file sizes and how they can be fixed. We discuss the tools you can use to optimize CAD file size and how you can maintain file efficiency during collaboration. Read on to learn more. 

Understanding CAD File Size

Native and non-native CAD files comprise various sections, each storing specific information. For instance, the DWG file format, a native file format, has four main sections: the header, classes, object data, and the object map. The header section contains information about the version of the DWG format, default units, project name, date and time when the file was created and modified, the coordinate system used, and more. 

The classes section stores information related to classes, while the object data section stores data about the graphical and non-graphical objects found in the drawing. The object map section captures the location of each object in the DWG file. Each section contributes to the overall file size, with the largest contributor perhaps being the section that stores information about the graphical and non-graphical entities. 

A typical CAD file is made up of general graphical 2D and 3D entities like lines, circles, splines, surfaces, blocks, and more, as well as software-specific information. Some of the software-specific information includes: 

• Cut lists, bounding boxes, and configurations in SolidWorks
• Embedded images in AutoCAD
• Linked files, sheets, families, and views in Revit
• Sections, elevations, preferences, elements, views, attributes, worksheets, layouts, libraries, and project notes in ArchiCAD

The list above isn’t exhaustive, but it clearly shows that different software applications store different types of data, which collectively contribute to the overall size of the files they output. The more data the software stores, the larger the CAD file becomes. A large file size isn’t always bad; for instance, large CAD projects are synonymous with large CAD files. A large file size is only a problem when it’s due to avoidable factors and hinders productivity. 

Causes of Large CAD File Sizes

Why do some CAD files grow to hundreds of megabytes or even exceed a gigabyte? There are several reasons why your file size might spiral out of control:

• Saving files in ASCII format instead of binary format: As we explain in our technical dissection of the DXF file format, binary DXF files take up 25% less space than ASCII DXF files and are, as a result, processed up to 5x faster. Evidently, ASCII files, which store data in plain text, are a relatively inefficient way of storing data. They can cause larger file sizes.
• Raster images embedded in your CAD file: Generally, raster images are large, meaning that if embedded as is, they increase the size of the CAD file.
• Unnecessary vector data in your CAD file: This data can include layers, blocks, lines, or styles that are not needed to display the vector graphics.
• Other unnecessary data and settings in your CAD file: As files are edited again and again, reams of settings and revision history can build up in the file. Much of this is not needed to display the drawing.
• Technical issues, such as converting between different versions of a file format

Issues Associated with Large CAD File Sizes

Keeping CAD file sizes manageable is crucial since large files can negatively impact productivity. The various problems that arise from a ballooning file size include:

1. Slow Performance

Large CAD files can take a long time to load. In some cases, these files may not load at all. They can also be unresponsive or lag unnecessarily. The issue is further compounded if your CAD workstation or laptop has low installed RAM. The software will inadvertently freeze whenever it takes up all the available RAM and may not function normally unless restarted. It can also crash, leading to data loss (especially if it was in the process of saving the file). As a result, your workflow is frequently interrupted, causing frustration and reduced productivity.

2. File Transfer Issues

Email platforms like Microsoft Outlook and Gmail limit the size of files you can send directly. If you want to send large files, you have to save them in a cloud storage drive and subsequently send a link to this file or use third-party solutions like WeTransfer. This, of course, creates more steps that can be avoided by optimizing CAD file size. 

Slow internet creates additional challenges when handling large CAD files. Sluggish internet makes it hard to upload and download large files, with downloads and uploads failing on a regular basis.

3. Difficulty in Data Management

Large CAD files contain a lot of information, some of which may be unnecessary. For instance, they may contain unused layers, blocks, configurations, and objects that only inflate the file size. This extra data complicates both working on the CAD model and managing essential information.

4. File Storage Issues

Large CAD files can deplete available storage, leaving little room for other files. This issue can affect both cloud systems and local drives. The secondary effect is that you may need to purchase more storage space, adding to the cost of a project.

Techniques for Reducing CAD File Size

You can use the following techniques to both optimize CAD file size and identify the causes, if any, of large file sizes:

1. Save As Command

The Save As command should act as the first step whenever you are looking to optimize CAD file size. This command sometimes creates a new file that takes up less storage space than the original one. This difference can arise from the original file storing unnecessary data that is not transferred to the new file. It can also be due to data corruption. In such an instance, you can use the new smaller file.

2. Use Lightweight File Formats

The Siemens Parasolid binary format (.x_b), being a binary file format, has a smaller file size. So, you can export files initially saved using formats that ordinarily take up more storage space, like .step and .shapr, as .x_b files. Alternatively, you can save such files using the binary DXF file format rather than the ASCII DXF file format. 

3. Use Built-in CAD File Optimization Commands and Tools

AutoCAD ships with a few commands that enable you to optimize CAD file size. These commands include Audit, Recover, and Purge. The Audit command prompts the software to assess the integrity of the CAD drawing and fix some of the errors it identifies. The Purge command deletes unused named items from the CAD drawing. These unnecessary items can include layers and block definitions. Lastly, the Recover command repairs a damaged or corrupted drawing file.

The Audit tool in Autodesk Revit helps you repair corrupted files or identify issues that cause the size of your file to balloon inexplicably. A successful audit can reduce the CAD file. But it is advisable to resolve all the warnings the audit tool identifies for the best results. This is because an excessive number of warnings can increase the file size.

4. Delete Unnecessary Data

You can use the following approaches to remove unnecessary data and, as a result, optimize CAD file size:

• Detach unnecessary Xref and image files: Xref and image attachments can be helpful whenever you want to create custom hatch patterns in AutoCAD, for example. However, they are largely unnecessary if you can achieve the same result using the available hatch patterns. In such an instance, you can optimize the CAD file size by detaching the Xref file.
• Remove unnecessary data like blocks, layers, configurations, unused components, and bounding boxes. The names of these datasets will depend on the software you are using. (It is advisable to save a copy of the file every time you remove this data to ascertain that it is indeed the culprit behind the increase in file size. Also, if you delete all the data yet the file size remains unchanged, that may indicate file corruption.)

5. Create Blocks for Repeated Objects

Sometimes, you may have to use the same collection of objects in different sections of your drawings. Instead of copying and pasting these objects every time you want to use them, you can create a block that contains all these objects. The advantage of this approach is that a block is stored only once, regardless of the number of times it is added to the drawing. In contrast, individual images are saved independently, substantially increasing the file size. Thus, using blocks helps you optimize CAD file size.

And as the role of AI in the CAD industry becomes more pronounced, software developers are introducing more AI-driven tools. Some of these tools can indeed help you reduce CAD file size. For instance, Autodesk introduced Smart Blocks, starting with AutoCAD 2025. Powered by machine learning, Smart Blocks is a set of tools that scans your CAD drawing to identify matching geometry, which it then converts into blocks.

6. Reduce Size of Embedded Raster Image Files

You can embed or attach raster images to CAD drawings. Such images do contribute to the overall size of the CAD file. For this reason, you can reduce the image size if you have embedded a raster image and wish to optimize CAD file size. Vectorworks, a popular BIM and architecture software, enables you to compress embedded image resources and bitmap images in a Vectorworks file. The software uses the JPEG compression method to optimize CAD file size.

You can also use non-CAD software. Software like Adobe Photoshop and Microsoft Paint enable you to reduce the size of a file. Alternatively, you can reduce its size by cropping the image, saving it using a different raster file format, or using software like Microsoft Word to save the image. Only after reducing its size can you embed the image into your CAD drawing. 

Optimizing 3D Models for File Size Reduction

Assembly and complex part files and BIM files can take up a lot of storage space. For instance, Revit models can be 2GB in size or more. And as stated earlier, such a large file size can cause a number of issues. In this section, we cover the approaches you can use to optimize CAD file size.

1. Reduce the Number of Polygons

CAD software uses techniques like tessellation to present 3D objects. This technique divides the surface of objects into polygons. The higher the number of polygons, the smoother the curves and the higher the resolution. By adjusting tessellation (polygon count), you can reduce resolution and file size. 

Software developers use different approaches to help you reduce the number of polygons. SolidWorks, for instance, lets you change the image quality by following these steps: click Tools > Options > Document Properties. Then, select the Image Quality option on the side menu. This option displays a slider under the Shaded and draft quality HLR/HLV resolution section, letting you choose your desired resolution (as shown in the image below). You can also change the resolution of wireframe images.

SolidWorks Document Properties Dialog Box

For its part, Fusion lets you use the Reduce command to reduce the number of faces on a mesh body. This command helps reduce the complexity of the drawing and, by extension, reduce or optimize CAD file size. To reduce the number of phases, click the Mesh tab and select Modify > Reduce. You will be prompted to select a reduction Type from the dialog box. You can choose to reduce the number of faces based on the Tolerance, Proportion, or Face Count. Similarly, Rhino’s ReduceMesh command helps you reduce the polygon count.

2. Simplify Parts and Assemblies

As we detail below, software like Inventor ships with tools that help engineers and designers simplify complex parts and assemblies. This tool simplifies complex assemblies or parts by creating a more lightweight file.

Using CAD Software Tools for File Optimization

Built-In Tools for Optimizing CAD File Size

1. Shrinkwrap or Simplify Command in Inventor

The Shrinkwrap tool in Autodesk Inventor (versions 2021 and earlier) creates a simplified part file from an assembly or complex part. It significantly reduces the file size for complex parts or assemblies. It simplifies files while preserving the original appearance of parts and assemblies.

Later versions of Inventor (2022 and later) sport the Simplify command. This command reduces the complexity of an assembly. Like the Shrinkwrap tool, Simplify creates a part from an assembly, helping you optimize CAD file size. However, it gives you more freedom by allowing you to specify the features and components you want the software to remove. 

2. Mesh Optimization Tools

As described above, software like SolidWorks, Fusion, and Rhino have commands that help you reduce the number of polygons. These tools optimize CAD file size by lowering the visual quality of 3D models.

3. Block-Creation Tools

Powered by Autodesk AI, the Smart Blocks feature in AutoCAD searches your CAD drawings for similar objects that it can convert into a newly defined block, a recently used block, or a suggested block from your Block libraries. By converting objects as blocks, which are saved only once rather than multiple times, such an AI tool helps optimize CAD file size.

For its part, BricsCAD has the BLOCKIFY command, which more or less performs the same function as the Smart Blocks. BLOCKIFY searches your CAD drawing and identifies similar 2D or 3D entities/repeated geometries. It then replaces them with block references. This tool dramatically reduces the size of your CAD drawing.

4. Built-In File Compression Tools

Software like ArchiCAD, Autodesk Fabrication, and SolidWorks, just to name a few, let you select an option to compress files. If you are using ArchiCAD, for example, the Options button in the Save dialog box lets you check the Compress filebox. According to Graphisoft, the creator of ArchiCAD, the file compression option reduces the size of the file by 60-70%. 

The SolidWorks’ Highly Compressed Graphics (HCG) translator compresses parts and assemblies, reducing the size of the CAD file. Such files are saved using the .hcg extension, which is optimized for transmission over the internet.

External CAD File Optimization Tools

1. Product Data Management Tools 

Product data management (PDM) tools like Autodesk Vault have file compression capabilities. The file compression feature in Autodesk Vault reduces the size of files sent between servers or between the server and the client. This way, the software makes it possible to transfer files faster, even over an internet connection with low bandwidth. In this regard, this file compression tool in Autodesk Vault optimizes CAD files for transmission (uploading or downloading) over the internet.

2. File Compression Software

There are a number of file compression software on the market today, from Winrar and WinZip to 7-Zip and PeaZip. Such software reduces file size by using different methods and algorithms that fall beyond the purview of this article. These tools also include encryption and password protection features that greatly enhance CAD file security.

Maintaining File Efficiency During Collaboration

You can implement the following measures, which will help you maintain file efficiency when collaborating with other professionals:

1. Use Cloud-Based Collaboration Tools

Cloud technology has made it possible to work from anywhere and collaborate on large-scale CAD projects. You can use cloud-driven tools like PDM and product lifecycle management software, common data environments (CDEs), and cloud-based CAD software to send large files securely. 

2. Maintain Consistent File Naming and Version Control Practices

A consistent file naming system avoids confusion. This practice, coupled with version control and revision, ensures that everyone is working on the latest version of a file. It also keeps to a minimum the number of files stored in the shared folder or vault, which, in turn, reduces your storage needs and associated costs.

3. Ensure Collaborators Use Same Software Build

As introduced earlier, different versions of a file format can cause an increase in the size of a CAD file. Oftentimes, this difference arises from using different builds of software. It is, therefore, advisable to ensure everyone in your team uses the same software to prevent this problem.

4. Overlay Objects and Images

Autodesk products like AutoCAD and Revit allow you to attach or link images and models using the external reference (xref) option. However, attaching the xref changes your drawing and increases the size of your current drawing, albeit slightly. To optimize performance, Autodesk recommends overlaying models or images rather than attaching them. In fact, overlaid xrefs are optimized for data sharing in a network environment.

Conclusion

Optimizing CAD file sizes helps you nip performance and productivity issues in the bud. Large files can slow down a computer or cause the software to crash. They also negatively impact data management, file storage, and file transfer. These reasons make a good case for optimizing CAD file size. CAD file optimization helps you to solve some or all of these issues. Fortunately, there are several approaches you can use to reduce the size of such files.

But beyond file reduction, it is always a good idea to identify any underlying issues that cause the file size to balloon unexpectedly and inexplicably. Such information helps you prevent recurrence. So, the various techniques for reducing CAD file size also help you identify some of the possible causes. We have also detailed how you can use software tools to optimize CAD file size as well as the measures you can implement to maintain file efficiency and avoid data corruption when collaborating with other professionals.