To view your app's CPU usage: Go to one.newrelic.com > (select an app) and see the CPU usage in the hosts list. The number of instances is listed under each host name (for example, 55 instances).
APM CPU percent usage measures aggregate CPU usage of all instances of your app or service on a given server. This percentage is affected by the number of instances running across cores on the server. Multiple instances of a service running on one server or in a multi-core environment can produce CPU usage percentages well above 100%.
APM calculates the percentage by aggregating CPU time and dividing by clock time:
CPU usage = (instance CPU time + instance CPU time + [...]) / (clock time)
Example: Upgrading to a quad core processor
If you upgrade from a dual processor to a quad processor under the same architecture, you should see roughly the same CPU numbers for the same loads and applications. If New Relic normalized the calculation, the upgrade would appear to produce an abrupt decrease in your CPU usage, even if the number of cycles you are using would be the same. Adding more instances does not make your code more efficient.