Calculating On-Demand Cost Equivalent from CUR for AWS Organization with Shared RI

Question

Hello AWS Community,

I am managing an AWS organization with multiple accounts, all sharing Reserved Instances (RI). For better financial analysis and reporting, I need to calculate the On-Demand cost equivalent for my EC2 instances from the Cost and Usage Report (CUR). My goal is to measure the Total Net Savings per linked account within the organization, rather than relying on the Total Net Savings from the Utilization report.

Specifically, I need guidance on the following points:

Extracting On-Demand Costs: How can I extract the On-Demand cost equivalent for each EC2 instance from the CUR?
Handling Shared RI Costs: Given the shared RIs across accounts, how should I attribute these costs to each account accurately?
Calculating Net Savings: What is the best approach to calculate the Total Net Savings per linked account by comparing On-Demand costs to the actual costs incurred, considering RI and Savings Plan usage?
Any detailed steps, best practices, or example queries would be greatly appreciated.

Thank you in advance for your assistance!

AWS-User-alantam · Accepted Answer

In a nutshell, you would need to generate a query that has line_item_usage_amount for each instance type that is covered by RI for each account. For OnDemand equivalent cost, you would have to calculate it using  line_item_usage_amount and public OnDemand pricing (you could use pricing_publicOnDemandRate I believe). Once you have OnDemand equivalent cost, the Net Saving would be the difference between OnDemand equivalent and reservation_effective_cost. This [query ](https://catalog.workshops.aws/cur-query-library/en-US/queries/compute#ec2-reserved-instance-coverage) could be used as a good start and always use [CUR Dictionary](https://docs.aws.amazon.com/cur/latest/userguide/data-dictionary.html) as a reference.

Calculating On-Demand Cost Equivalent from CUR for AWS Organization with Shared RI

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