Hyper-V RAM Calculator

This download has been superseded by a newer Hyper-V Calculator spreadsheet.

I’ve previously discussed how RAM is used by Hyper-V in terms of:

• The parent partition
• Hyper-V services
• Drivers
• Guest RAM allocation overhead.

I’ve put together an Excel spreadsheet that calculates how much RAM is consumed by a VM as you load it onto a host.  Using it is easy:

1. Specify how much RAM is in the physical host machine.
2. Add each guest VM and enter how much RAM (in GB) you want to allocate to the guest.
3. The RAM utilised by the guest is calculated and the amount remaining on the host is presented.

The numbers you need to enter are highlighted in yellow.

The formula used assumes maximum RAM overhead, i.e. the worst case scenario of 32MB for the first GB and 8MB for each GB after that on a per VM basis.  I’m also allowing 300MB in addition to the 2GB recommended as the reserve for the parent partition.  Often, this can be considered a part of the 2GB.  You can recalculate things by adding in another line item to specify driver requirements for the parent OS if you want.

EDIT:

I’ve done some testing on hosts with 32GB RAM and the theory seems to match the practice.