How is RDS/EC2 Projected Cost for Current Month calculated?

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• CloudHealth

Issue/Introduction

The formula for this field is Total_MTD_cost + (Remaining_Hours_in_Month * (Total_MTD_Cost / Total_MTD_Hours)) = Projected Cost for Current Month

 

Total MTD Cost and Total MTD Hours can be pulled from the EC2 Instance Hours report or RDS Instance Hours report respectively via the following fields:

 

Total MTD Hours = Total Hours
Total MTD Cost = Total Cost

The Remaining Hours in Month field is calculated based on the current day, in order to determine this number you can rearrange the equation above -

E.g. using example values below:

Total MTD Cost = 58.33
Total Hours = 0.4581
Projected Cost for Current Month = 25654.56

58.33 + (Remaining Hours in Month*(58.33/0.4581)) = 25654.56

1. Simplify equation first by dividing Total MTD Cost by Total Hours = 58.33 / 0.4581 = 127.330277232

2. This leaves us with 58.33 + (Y * 127.22549687) = 25654.56

3. Subtract Total MTD Cost from both sides of the equation Total MTD Cost and Projected Cost for Current Month - Y * 127.330277232 = 25654.56 - 58.33 resulting in Y * 127.330277232 = 25596.23
4. Finally divide both sides by 127.330277232 resulting in Y = 201.022337785

5. Plugging that into the original equation = 58.33 + (201.022337785*(58.33/0.4581)) = 25654.56