# How to calculate the number of hours covered by EC2 Instance Savings Plans

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I am using EC2 Saving Plans for 6 instances. In the bill, I see On Demand Linux Instance Hour (hrs) and usage covered by EC2 Instance Savings Plans (hrs). I wonder how I can calculate the usage covered by SP. For instance (on August):

• Commitment: \$0.42400/hour
• \$0.125 per On Demand Linux m4.large Instance Hour: 4,464.000 Hrs (= 6 x 24 x 31)
• m4.large Linux instance usage in ap-southeast-1 covered by EC2 Instance Savings Plans: 4,393.599 Hrs
• SP rate: \$0.07400
• On-Demand rate: \$ 0.12500
duyl97
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You stated that your Commitment - \$0.424/hour

Hence if you run your 6 servers for 24 hours per day over the course of 1 month and wish to use SP to cover all the running hours (i.e. 100% coverage) You will need to purchase \$0.074 (SP Rate) X 6 = \$0.444/hour as a commitment to attain 100% on the savings plan.

What you see currently covered by EC2 Instance Savings Plans: 4393.599 Hrs was due to the purchased SP commitment/hour which didn't cover the entire 4,464 hours in that month hence the rest of the hours not covered by the SP (~70.4 running hours of the 6 instances) will be charged at On-Demand rate of \$0.125/Hr.

Hope the above helps!

Ray T
• Many thanks for your answer. I'm agree that 6 instances exceeded the commitment and be charged with On-Demand rate. I'm just confused if I could calculate the number of hour covered by SP or not. That will be useful when I plan to use more instances within the family instance.

• To understand if your current commitment/hour is able to be covered by SP or not - simply take the 2 numbers and multiply by number of hours in a month like below -

( Current commitment per hour / (SP rate of Instances * quantity) ) * number of hours in the month Taking example above

( \$0.424 / (\$0.074 * 6) ) * 4,464 hours = ~4,262.91 hours covered by SP in that month.

SP cover per hour utilizations, hence should not be calculated as a per month but rather by looking at per hour coverage if you are looking to cover 100% under Savings Plans.

• Thanks for your info. That makes sense to me.