Home > RAM, Windows > Calculate How Much RAM Memory You Need for Autodesk Revit 2011

Calculate How Much RAM Memory You Need for Autodesk Revit 2011

Autodesk Revit 2011 optimized file loading by using multiple CPU threads to transfer model data to RAM; maximizing the use of computational resources required to open a model. Since the slowest performing hardware in a computer is often static data storage, usually a hard drive, Revit employs an “in memory” data model, taking advantage of much faster RAM to manage the model in an editing session. Due to the constricted performance represented by hard drive access, it is recommended, that whenever possible, to prevent the underlying Windows operating system (OS) from caching active model data to the hard drive.

To understand how much RAM a given model will use in a typical editing session, check the size of the RVT file on disk. Because an RVT file on disk is highly compressed, loading the model into memory requires an expansion process. As a result, Revit uses roughly 6 times as much RAM as the size of the RVT file on disk. As users open views, add and change elements, additional expansion takes place, typically topping out at a memory use of approximately 20 times the RVT’s size on disk. These factors can vary with the complexity of the model, but often they provide good guidelines to understand how a Revit model will reside in RAM. Looking at a common workstation configuration with 8GB of RAM, we can calculate the approximate size of a model that can reside in memory:

8GB – 1GB (OS) – 1GB (video and other drivers) = 6GB / 20 = ~300 MB model on disk

Different modeling techniques can vary the division factor of 20 somewhat, but in general this formula provides a good guideline to understand when you’d expect a model to perform optimally through complete memory residency.

One exception to this rule occurs on Revit model upgrade, say from Revit 2011 to Revit 2012. Where a typical editing session will only require the expansion of some elements of the model, an upgrade requires the expansion of all model elements, resulting in higher memory use or increased swapping to hard drive by the OS. For this reason, the one-time upgrade operation requires more processing time than subsequent file opens.

Considering the inevitable trade-offs when specifying a new workstation, maximum performance can be achieved by including enough RAM to fully load a typical model into memory, enabling Revit to take the best advantage of the Windows platform.

Author: Anthony A. Hauck, Revit Senior Product Line Manager, Autodesk AEC Solutions Division

  1. April 15, 2011 at 3:47 pm

    Thanks for the info! I’ve seen that “formula” before, but I’ve noticed that 8GB is almost at the low end of the spectrum. Since users always have other software open (Outlook, AutoCAD, IE, etc etc), our Revit users are always hungry for more RAM.

    Quick question: do you know how the new Revit 2012 communicates as far as communication back to the server? I’ve been told “it’s been improved and optimized” but are there any specific numbers? I’m using this to derive a formula for Revit Server and network optimization. Thanks!

    • April 28, 2011 at 6:53 pm

      Revit, as an authoring application, communicates with Revit Server via the TCP protocol. One major improvement is enhanced reliability over higher latency connections. The TCP protocol is far more fault-tolerant than typical file protocols designed for low- or zero-latency connections. The quantity of data transferred is unchanged from earlier versions of Revit, and is entirely dependent on the number of changes in the user’s model, coupled with the changes received from other team members.

      • Ric
        September 26, 2011 at 3:12 pm

        The communication back to the server was superb. my problem was eradicated within a few minutes.

  2. Kasey Robinson
    January 14, 2013 at 8:00 pm

    I am working with a file that is 30,000KB and I have 3 links that are loaded at any given time. 2 point cloud files that are 6KB each and a CAD link t hat is 12 KB. I have 32GB of RAM and my Revit session is tellind me its running out of RAM. I am not sure if this is “normal” for a file of this size but it seems to me that something is wrong with my machine. Does anyone have any suggestions?

  3. Tony
    February 15, 2013 at 10:31 pm

    Anthony: Thank you for posting & explaining this!

    I need to figure out how much RAM will be needed for a specific Revit project.

    Would this x20 rule also apply to Revit files linked in to my host file? For example, I’m working in my Architectural Interiors file (300 MB), but I also need to link in the Core/Shell Revit file, the Lighting file, the Plumbing file, etc. (assume all others 150 MB).

    Should I multiply ALL of these files times 20? or just the host file?


    • Anthony A. Hauck
      March 4, 2013 at 11:46 pm

      Hi Tony.

      Linked files are a more efficient, since we don’t have to expand the Elements entirely, because you won’t be editing them n the same session. So, in short, you shouldn’t multiply the total size of all the models on disk by 20. Multiply the host model’s disk size by 20, then add up all the linked model sizes and multiply by… some unknown factor that I’ll have to check on tomorrow — stay tuned. (Sorry to keep you in suspense, but I saw this too late to check with development).


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