Displaying counter metrics

I need help dealing with ‘counter’ metrics. Basically I am querying network interface stats. As part of this I have metrics ‘BytesIn’ and ‘BytesOut’. Both of them are counters, and doesnt represent the bandwidth, which I am looking for. This counter value keeps increasing. How do I convert this to Mbps or Gbps and represent in the graph?

Did you ever get any feedback regarding this?
I am in the same situation.