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VM Memory Ballooning Calculator

Work out vm memory ballooning instantly with clear inputs, formula shown and shareable results.

About VM Memory Ballooning Calculator

The balloon driver inflates inside the guest so the guest's own kernel chooses which pages to release, which is far better than the hypervisor swapping blindly. It works only while guests hold genuinely idle memory: once active demand exceeds host RAM, ballooning forces guest swapping and performance collapses.

Formula

Ballooning requirement

available for guests = host memory - hypervisor reserve; reclaim = allocated - available; active demand = allocated x active share

Worked example

With the default values below, VM Memory Ballooning Calculator returns Memory the balloon driver must reclaim of 158.7. Change any input above and every figure here is recalculated in your browser.

Inputs used

Host physical memoryminimum 1 GB
512 GB
Memory allocated to VMsminimum 0.1 GB
640 GB
Share of guest memory actively usedaccepts 1–100 %
55 %
Number of VMsminimum 1
40

Results

Memory the balloon driver must reclaim
158.7 GB
Reclaim per VM
3.97 GB
Actively used guest memory
352.0 GB
Assessment
Ballooning can reclaim idle memory safely

Step by step

  1. 1Values used
  2. 2Ballooning requirement
  3. 3Memory the balloon driver must reclaim= 158.7 GB
  4. 4Reclaim per VM= 3.97 GB
  5. 5Actively used guest memory= 352.0 GB
  6. 6Assessment= Ballooning can reclaim idle memory safely

Assumptions and limits

  • The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

Why is ballooning better than host swapping?

The guest kernel knows which pages are cold. The hypervisor does not, so host swapping frequently pages out memory the guest is about to use.

Should the balloon driver be disabled for databases?

Reserving memory rather than disabling the driver is the better approach, so the hypervisor never targets that VM for reclamation.

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