Overview

Compute credits are calculated based on a job's duration and its resource class.
The total duration billed for a workflow is based on the duration of each job in the workflow.

We can verify the total duration each job took, for a given workflow.
This may be useful for estimating a workflow's billable compute credits.

Fetching duration information 

Here is a simple script that uses our CircleCI API to calculate each job's duration:
https://gist.github.com/kelvintaywl/726ab96f4d2eb26193512b29a22e9f0f

To use this script, you can download it and run the following

# script requires curl & jq
# NOTE: please set your CircleCI API token under $CIRCLE_TOKEN

$ sh ./calculate.sh <workflow ID>

Outcome

You can see each job's duration for a given workflow from the script output.

# Example
$ sh ./calculate.sh 481961c0-5fb5-4759-810c-2c301445c2c0

For Workflow ID 481961c0-5fb5-4759-810c-2c301445c2c0:
job gh/kelvintaywl-cci/cci-shells/job/45 took 2524 ms.
job gh/kelvintaywl-cci/cci-shells/job/43 took 190409 ms.
job gh/kelvintaywl-cci/cci-shells/job/42 took 2170 ms.
job gh/kelvintaywl-cci/cci-shells/job/44 took 4951 ms.
job gh/kelvintaywl-cci/cci-shells/job/46 took 2395 ms.

Additional Resources: 

• Resource Classes