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Azure VM Right-Sizing Calculator

Size an Azure VM down to the vCPU and memory it actually needs from observed peaks plus a headroom target.

About Azure VM Right-Sizing Calculator

Right-sizing converts an observed peak into an absolute resource demand, then divides by the utilisation you are willing to run at to get the size you need. Because Azure sizes come in fixed vCPU steps the answer is rounded up to the next step, and the memory-per-vCPU ratio of the family can force a larger size than CPU alone would. Averages hide spikes, so sizing on the 95th percentile with explicit headroom is the difference between a saving and an outage; validate the projected price against the Azure pricing calculator because cost does not always scale linearly with vCPU across families.

Formula

Azure VM Right-Sizing

required vCPU = current vCPU × peak CPU% ÷ target utilisation%, rounded up to the next Azure size; memory is checked the same way against the family's GiB-per-vCPU ratio.

peak CPU%
95th-percentile CPU from Azure Monitor, not the average
target utilisation%
Peak you are willing to run at, leaving spike headroom
ratio
New vCPU count divided by the current count, used to scale cost

Worked example

With the default values below, Azure VM Right-Sizing Calculator returns Recommended vCPUs of 4. Change any input above and every figure here is recalculated in your browser.

Inputs used

Current vCPUsaccepts 1–416 vCPU
8 vCPU
Current memoryaccepts 1–4,096 GiB
32 GiB
Observed peak CPUaccepts 1–100 %
22 %
Observed peak memoryaccepts 1–100 %
45 %
Target peak utilisationaccepts 20–95 %
70 %
Current monthly cost per VMaccepts 0–100,000 USD
280 USD
VMs in this roleaccepts 1–5,000 VMs
6 VMs

Results

Recommended vCPUs
4 vCPU
Recommended Memory
32 GiB
Projected Monthly Cost
$1,680.00
Monthly Saving
$0.00
Saving
0.0%
Recommendation
Correctly sized for the observed peak

Step by step

  1. 1Values used
  2. 2Azure VM Right-Sizing
  3. 3Recommended vCPUs= 4 vCPU
  4. 4Recommended Memory= 32 GiB
  5. 5Projected Monthly Cost= 1,680.00
  6. 6Monthly Saving= 0.00
  7. 7Saving= 0.0
  8. 8Recommendation= Correctly sized for the observed peak

Assumptions and limits

  • The result is derived only from the 7 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax 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

How is Azure VM Right-Sizing calculated?

required vCPU = current vCPU × peak CPU% ÷ target utilisation%, rounded up to the next Azure size; memory is checked the same way against the family's GiB-per-vCPU ratio. Right-sizing converts an observed peak into an absolute resource demand, then divides by the utilisation you are willing to run at to get the size you need. Because Azure sizes come in fixed vCPU steps the answer is rounded up to the next step, and the memory-per-vCPU ratio of the family can force a larger size than CPU alone would.

Why does Azure VM Right-Sizing matter?

Averages hide spikes, so sizing on the 95th percentile with explicit headroom is the difference between a saving and an outage; validate the projected price against the Azure pricing calculator because cost does not always scale linearly with vCPU across families.

What values do I need to enter?

This calculator takes 7 inputs: Current vCPUs, Current memory, Observed peak CPU, Observed peak memory, Target peak utilisation, Current monthly cost per VM, VMs in this role. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.

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