How to calculate containers' cpu usage in kubernetes with prometheus as monitoring?

This I'm using to get CPU usage at cluster level:

sum (rate (container_cpu_usage_seconds_total{id="/"}[1m])) / sum (machine_cpu_cores) * 100

I also track the CPU usage for each pod.

sum (rate (container_cpu_usage_seconds_total{image!=""}[1m])) by (pod_name)

I have a complete kubernetes-prometheus solution on GitHub, maybe can help you with more metrics: https://github.com/camilb/prometheus-kubernetes

I created my own prometheus exporter (https://github.com/google-cloud-tools/kube-eagle), primarily to get a better overview of my resource utilization on a per node basis. But it also offers a more intuitive way monitoring your CPU and RAM resources. The query to get the cluster wide CPU usage would look like this:

sum(eagle_pod_container_resource_usage_cpu_cores)

But you can also easily get the CPU usage by namespace, node or nodepool.