At some point your Revit project size may have dramatically increased without the project itself dramatically changing.  I’ve included 4 items below which are frequent causes for this type of file size change:

1.  Family Types

Look for a large number of families which may be loaded into the project.  Also if a type catalog was used when families were loaded into the project, there may be a large number of unused types.

Related to this, 1 family instance may have several nested family instances.  So in the Project browser it may appear as 1 family but could potentially contain 4 or 5 more nested families.  This can easily magnify the project size and is something to look for if there has been an increase.  Manage > Purge Unused can be used to remove any unused family types.

2.  Detailed Model Fill Patterns

Model fill patterns containing a large number of segments will greatly increase a Revit project size.  This typically occurs when a detailed hatch pattern [.pat] file is used to define a new fill pattern.  If when possible avoid the use of detailed custom model fill patterns to optimize the file size.

3.  Raster Images & Rendered Views

For every inserted image or rendered image saved to the project, the project size will increase.

All of the inserted images, along with an instance count, can be viewed under Insert > Manage Images.  Unneeded images can easily be deleted from this menu using Delete.

For rendered images saved to the project, by default they will be saved under the Renderings Project browser organization.  They appear under the Manage Images dialog as well.

4.  Lack of Compact File & Audit

It is essential to frequently open the central file, or project file with Audit checked to ensure the database is optimized.  Along with this the project file should be compacted on a regular basis.  For example audit and compact file should be run at least once a week.

To do this when opening a central file, ensure Audit is checked.  Once the central file is open, save the project through Collaborate > Synchronize and Modify Settings > check Compact Central File.

For a non-worksharing enabled project file you can re-save the project file through R > Save As > Project.  Click Options and check Compact File.