Instance pricing calculation


Im new to Amazon AWS and currently on the free tier. I thinking of adding a higher on-demand instance, but the pricing calculations on instances are a bit confusing. It says for example, the c5a.large is $0.139 per hr on-demand. If I take an additional 60gb of Gp3 storage within limits, thats an additional $1.75. Cost of windows server is about $4. But there is some mention of on-demand instance hours that I dont fully understand. If I select 3 hours a day on daily spike traffic, 3x per week, that comes to 36 hours a month. But the on-demand instance hours is calculated based upon 351.9642 hours, bringing the total to $51.55 a month?

asked 2 months ago155 views
2 Answers
Accepted Answer


I think there is something wrong with the calculation method.
I thought that if you want to run it for 3 hours a day, 3 days a week, you need to make the following choices.
"Usage" is calculated as 9 because it runs 3 hours a day and 3 days a week.

If you would like to find out more about charges, we recommend that you open a case with AWS Support under "Account and billing".
Inquiries under "Account and billing" are free of charge.

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answered 2 months ago
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reviewed a month ago
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reviewed 2 months ago
  • The calculation is like this. b

  • I think the usage of Daily spike is different. Daily spike is a method of calculation that assumes that spikes will occur, so I think it is a calculation method when increasing the number of instances to cope with spikes. I don't think this is the calculation method used when stopping EC2 on a daily basis.

  • Clear enough. Thank you.


I was adding the daily figures under the EC2 specifications daily spike traffic and had the compute saving plan turned on by default. Still it should come to the same result. But its displaying a different figure. Also 9 hrs a week monthly comes to 36 hours. How is the 39 hours derived?


answered 2 months ago
  • Also 9 hrs a week monthly comes to 36 hours. How is the 39 hours derived?

    There aren't exactly four weeks in a month.

    AWS will work out the figures as 9 hours per week => avg 9/7 hrs per day => 9/7 * 365 hrs per year => 9/7 * 365 / 12 hrs per month = 39.107

  • Got it. Thanks a ton.

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