The Microsoft Exchange team has released the Exchange 2013 Server Role Requirements calculator.

From the MS Exchange Team blog:

It’s been a long road, but the initial release of the Exchange 2013 Server Role Requirements Calculator is here. No, that isn’t a mistake, the calculator has been rebranded. Yes, this is no longer a Mailbox server role calculator; this calculator includes recommendations on sizing Client Access servers too!

I recommend reading the rest of that post because it does outline some very interesting things about Exchange 2013 sizing.

Download the calculator here.


About the Author

Paul Cunningham

Paul is a former Microsoft MVP for Office Apps and Services. He works as a consultant, writer, and trainer specializing in Office 365 and Exchange Server. Paul no longer writes for


  1. Nima

    Hi Paul.
    I use the calculator for our environment based on Exchange 2016.I want to have 2 copy of each database so I entered it as input.The calculator recommends 4 mailbox server with DAG consists of all server.I want to know what is benefit of having 4 server while we have only 2 copy of each database among them.I know that if one server fails another could do the failed server duties and also host the database copy but does failing two ( or more in other senarios without administrator reaction to failure) servers at a same time happen to much?
    Thank you.

    1. Avatar photo
      Paul Cunningham

      There’s a lot of variables in that calculator so it’s hard to say why it is giving you a specific recommendation when I can’t see the inputs you provided.

      The short answer is, that the calculator tends to recommend solutions that are aligned with the Preferred Architecture for Exchange (Microsoft has published this on their blog if you want to read it).

      1. Nima

        Thanks Paul.
        The input name is “Total Number of HA Database Copy Instances (Includes Active Copy) within DAG”

        1. Avatar photo
          Paul Cunningham

          No, that’s not what I mean. I can’t see what you’ve entered or chosen in all the different fields of the calculator, so I can’t tell you why it’s telling you something.

          What I can tell you is that Microsoft publishes the Preferred Architecture for Exchange, which recommends four database copies across four DAG members, and that is what the calculator will often recommend you deploy as a best practice. You can read the Preferred Architecture for details on why they recommend that.

          1. Nima

            Oh Ok.Thank you so much Mr Paul

Leave a Reply