How to calculate the year cost of an AWS reserved instance with partial upfront payment

amazon-web-servicesreserved-instances

I'm not understanding how the partial upfront work for ec2 reserved instances. I'm trying to calculate how much the instance will cost on one year.

If, for example, I add an m4.xlarge instance reserved for one year with partial upfront on AWS Calculator it returns the following information on the estimate tab:

Amazon EC2 Service (US-East): 702.02
– Compute: 54.02
– Reserved Instances (One Time Fee): 648.00

Total One-Time Payment: 648.00
Total Monthly Payment: 54.02

My doubt is if the monthly payment is included in the first month.

Should I calculate the cost of an entire year as 648 + 12 * 54.02?
Or the cost is 648 + 11 * 54.02?

Thanks

Best Answer

Full year (x12). Amazon's cost-model doesn't pre-pay hourly costs like that. It's either up-front one-time, or hourly. No middle ground.