If we navigate to our Service Bus namespace workspace in the portal and click on the TOPICS tab, we can see a quick overview of our topics, including their status, stored message size (CURRENT SIZE), and capacity (MAX SIZE):
Now, if we click on the topic and navigate to its workspace, we have a DASHBOARD section, which gives us a quick overview of the topic status with a graph that shows the messaging metrics, and a usage overview, which shows us how much of our storage allowance we're using along with some quick glance information.