How Much RAM Should I Get

I get this question quite often from many people, whether they are looking to get a new computer or looking to make some updates to their current computer.  Here’s a little excerpt from the Revit  Model Performance Technical Note…

“Please keep in mind the amount of local machine RAM required is approximately 20 times the size of your compacted central project file.  Each linked file would apply to this total as well.”

What this really talks about is how much RAM is required to OPEN a Revit file.  So if you have a 100MB Revit file (I like easy math!), you’ll need 2GB of available RAM to open that file.  Got a 100MB Revit Structure file linked into the Arch file, better have 4GB of available RAM when you open the Arch file.  Notice, I’m not saying that you need “X” amount of installed RAM, it’s “X” amount of available RAM  to open a Revit file.

Because of this requirement, I’ve been recommending that people utilize a 64bit OS so you can get at least 6GB of RAM installed, but preferably 8GB of RAM.  Unless you are working on small projects and you’re Revit files are going to hover around 50MB or less, then you could get away with 4GB of RAM and potentially a 32bit OS.

Sending Revit Files to Consultants

I had an interesting call the other day with an Electrical designer that received an Architectural file from the firm they were working with.  The arch file was over 275MB and they had trouble linking the file into their MEP file.  They tried opening the file to see if they could even open it...but they got the system memory errors and couldn't open the file.  They finally were able to open the file on someone's pc without memory warnings, but when they attempted to save it though, no go.  So I had them do a Purge Unused and then try to save it...which worked.  When we checked the new file size, it went down to ~45MB!!  This file of course could then be linked into the MEP file without trouble.

So what's the point of this you may ask?  When you are sending files out to your consultants, do them a favor (not to mention yourself) and do a little cleanup!  Even if you don't want to purge your working file, detach a copy (if it's a central file) and purge that copy.  It will save time copying the file to the FTP site or whatever you are using to share your files and potentially save your consultants some headaches!  Or, the call from them saying they can't use your file!

Nested Familes and File Size Test

A few weeks ago, a colleague of mine (David Lidbury) and I were having a discussion regarding nested families and their effect of the size of a project. We both had initially heard that nesting families wasn’t the best thing to do as it increased the file size, but neither one of us actually have run across that problem. We both have utilized nested families with customers and didn’t have any trouble. So, David did some testing to see what would happen to a file’s size if he built a door that was made of nested components versus a door that wasn’t. The results were a little surprising….

The set up

240kb Door without nested parts
HM door frame with the same parameters as listed below but with all the needed parts (Panel, Plan & Elevation swing) in the same family file.

316kb Door with nested parts
HM door frame with parameters to allow for full flexibility (Separate Fame Head and Jam parameters, etc.). This file is the base for the full family file. Nested families included; Door Panel, 2D Plan swing, Elevation plan swing

Conclusion #1 – The family size with nested parts is 76kb larger


Test - 1
I created a 22,000sf building then saved it as two separate files. I then added 36 doors of each type in there respective files.

1,208kb 36 doors without nested parts
1,308kb 36 doors with nested parts

Conclusion #2 – The file size with nested parts is 100kb larger


Test – 2
I added 99 additional levels and copied the first level up 99 times. This resulted in a door count of 3,564.

14,972kb 3,564 doors without nested parts
14,884kb 3,564 doors with nested parts

Conclusion #3 – The file size with nested parts is 88kb Smaller. This is obviously a surprise (and I did double check which file was which). The file size actually gets smaller as more nested families are added.


Of course this was a very simple project with mainly walls and doors. But, even with taking the project further and adding all the other components a building would have, the family built from nested components really doesn’t have an effect on the file size.