VM memory budget worksheet

Compare configured guest RAM with host capacity and your own reserve. A free, account-free Proxmox RAM allocation calculator that runs on this page.

Set your host budget

Inputs stay in memory on this page. Nothing is saved, sent to a server or placed in a URL. Download creates a local plain text report.

Host RAM

Host RAM unit

Your host reserve

Reserve unit

Choose your own allowance for the host OS, caches, hypervisor and workload overhead. The example's 8 GiB is illustrative, not a recommendation or admission limit. A reserve larger than the host is allowed and shows a deficit.

Configured guest allocations

Use decimal points, up to 6 decimal places; no thousands separators. Host RAM must be positive. Reserve and allocations may be zero. Each amount is limited to 1,048,576 GiB or equivalent; up to 100 guests.

Duplicate names count as separate rows. Empty names appear as “Unnamed guest”. Names are literal text, up to 80 characters.

Worked example: a 64 GiB host, an illustrative 8 GiB reserve and two 16 GiB guests.

Total guest allocations: 32 GiB
Planned commitment, including reserve: 40 GiB
Signed allocation headroom: +24 GiB

Allocation headroom after your reserve. This is not measured free memory or a guarantee that a workload will fit.

2 guest rows; duplicate names count separately.

Guest 1: Application — 16 GiB
Guest 2: Database — 16 GiB

Negative headroom is a signed planning deficit, not an OOM prediction. Positive headroom does not prove that active workloads will fit. Results display in GiB, rounded to 6 decimal places; tiny nonzero values remain labeled.

Configured, active and ballooned memory differ

Configured RAM is the guest allocation you choose to budget. For a VM with a minimum and maximum, enter the configured maximum if planning for all guests to reach their limits. Each row is counted independently, even if a guest is currently stopped.

Active memory describes current workload use, which changes over time and depends on the measurement. This worksheet does not read host or guest metrics and cannot infer active use from configuration.

Ballooning can adjust memory available to a guest when the hypervisor, guest driver and configuration support it. A lower current allocation does not erase the configured maximum from a capacity plan. This calculation makes no assumption that memory can be reclaimed.

Review your actual configuration and workload before changing allocations. See the Proxmox VE memory documentation for configuration details. This worksheet does not call Proxmox or change infrastructure.

Formula and explicit units

Guest allocations = sum of every configured guest row.
Planned commitment = host reserve + guest allocations.
Allocation headroom = host RAM − planned commitment.

Example: 64 GiB − 8 GiB − (16 GiB + 16 GiB) = +24 GiB. Changing the guests to 32 GiB each gives 64 − 8 − 64 = −8 GiB, a deficit. With no guests, 64 − 8 = +56 GiB.

GiB and MiB use binary units: 1 GiB = 1,024 MiB = 1,073,741,824 bytes. GB and MB use decimal units: 1 GB = 1,000 MB = 1,000,000,000 bytes. Mixed inputs are converted before adding; for example, 16 GiB + 16,384 MiB = 32 GiB. Dates and daylight-saving time do not affect memory quantities.

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