By default, every Windows Azure subscription has a limit of 20 compute cores. This applies to both VMs (IaaS) and worker roles (PaaS). Fortunately this is a soft limit and you can increase it by submitting a support ticket to the Windows Azure team through the management portal here. The following table lists the number of cores for each available Windows Azure instance:

To see how many cores each of your cloud services are using just look in the management portal. You will se something like this:

Unfortunately you need to manually add all the cores for each cloud service to get the total number. To work around this limitation you can use PowerShell:

https://gist.github.com/morgansimonsen/8039470

Save the above as a PowerShell script and run it from a prompt with the Windows Azure PowerShell module added. It will return all your VMs, sorted by name, their instance sizes, the number of cores they each use and the total number of cores in use in your subscription.

If you are paying for your Windows Azure subscription with a credit card your credit limit is $15000 by default. This will let you increase to a total of 175 cores in your subscription. If you want more cores and still pay with a credit card you will have to go through a credit check process to increase your credit limit. If you move to an Enterprise Agreement there will be no need for any credit checks to increase your core count beyond 175.

For large deployments the Windows Azure Capacity Planning team will want information from you so that they can allocate the required resources in the regions you specify. Typical questions they will ask you is where (region) you want to deploy, if you can deploy in several regions, if you are creating a new deployment or growing an existing one, which VM sizes you require and other services, like CDN, SQL etc) that you may require.