How to estimate memory and number of CPU for an ASP.NET Application

What is the response time about? And the concurrences?
What is the version of the Operating System? It's a 32 bit or 64 bit architecture?
What edition of SQL Server is installed? It's a 32 bit or 64 bit architecture?
How big is your database? And how big is estimated to be?
The SQL Server it's a dedicated machine? How many SQL Server instances exists in the machine? There's more database in the instance?
The machine is virtual or physical?

You can use load tests to see how your application would behave in different environments.

See Creating and Editing Load Tests

hi Vitor,

Please find my answer below and looking for your suggestion:

What is the response time about?  : Response time is 2 seconds/request
And the concurrences?: About 400 concurrences
What is the version of the Operating System? : Windows server 2008 64 bit
It's a 32 bit or 64 bit architecture?: 64bit version
What edition of SQL Server is installed? It's a 32 bit or 64 bit architecture?: MS SQL 2008 R2, 64 bit
How big is your database? And how big is estimated to be? : 32 GB, Increase 3G per months
The SQL Server it's a dedicated machine? : Dedicated machine
How many SQL Server instances exists in the machine? There's more database in the instance?: only one instance.
The machine is virtual or physical?:  virtual server

Thanks and Regards,

What is the response time about?  : Response time is 2 seconds/request
 And the concurrences?: About 400 concurrences

That was you said before. My question was what is the response time? It's the response for what kind of request?
Same for the concurrence question. Which kind of concurrence are you talking about?

Being a virtual server by now you can't give more than 4vCPU, so I would suggest the maximum for SQL Server.

For the memory, depends what amount of data you need to be ready for immediate access. In the limit you'll need to have full DB available (live data) so at least 32GB. But imagine that half of the data are only for historical purpose so they don't need to be always available for increase the read performance, so in this case you'll need only 16GB of RAM. Do you see what I mean?

And I'm assuming that you have only this database in the SQL Server because you didn't answer if there's more database in the instance.

Hi Vitor,

Thanks for your helps.

For response time, I mean reponse time for any request from user.
For concurrence , I mean number of users using system in the same time.
We have only one database running in DB Server.

Thanks and Regards,

Hi Vitor,

Right, 2 seconds response time is the maximum time allowed to response for a request.

I also think that its depend on design. But with 32 GB RAM and 4 CPU, Do you think its suitable ?

Thanks and Regards,

I think it is but only you can verify that.
Being a VM you can change the configuration quickly.

Thanks Vitor for suggestion.
I do as your comments

NguyenTuanHung,

Thanks Vitor for suggestion.
I do as your comments

Do you need help closing the question?

Thanks Anthony,
I think we can close this question.

Regards

This is how it is done:
How do I accept a comment as my solution?