How to see how much of our purchased bandwidth we use at my work?

What would be the best way to see CORE uplink bandwidth utilization?

Long story short we have a 500mbps up/down dedicated fiber and I'm being asked by management if that is overkill or not. I'm hoping to find a way to see real time usage on that interface so I can get a better idea of whether 500mbps is to much bandwidth for us or just enough.

We use palo alto firewalls, and I also have solar winds at my disposal if that helps