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Azure Kubernetes Service (AKS) Calculator

Size AKS node pools from pod requests, applying Azure's CPU and memory reservations and the pods-per-node ceiling.

About Azure Kubernetes Service (AKS) Calculator

AKS reserves node resources on a sliding scale — 25% of the first 4 GiB of memory, 20% of the next 4, 10% of the next 8, 6% of the next 112 and 2% beyond, plus a 750 MiB eviction threshold — so a 16 GiB node schedules roughly 12.5 GiB of pods. The node count is then the worst of three independent constraints: CPU requests, memory requests and the pods-per-node limit that Azure CNI defaults to 30. The pods-per-node limit is set at node-pool creation and cannot be changed afterwards, so a cluster sized only on CPU and memory can run out of IP-backed pod slots at a third of its capacity; the control plane itself is free on the Free tier, meaning almost the whole AKS bill is ordinary VM cost.

Formula

Azure Kubernetes Service (AKS)

nodes = max(pod CPU ÷ allocatable CPU, pod memory ÷ allocatable memory, pods ÷ usable slots), where allocatable memory subtracts 25%/20%/10%/6%/2% of successive memory bands plus a 750 MiB eviction threshold.

allocatable
Node capacity left after kubelet and system reservations
usable slots
Pods-per-node limit minus the DaemonSet pods every node runs
eviction threshold
750 MiB AKS holds back so the kubelet can evict before the node stalls

Worked example

With the default values below, Azure Kubernetes Service (AKS) Calculator returns Nodes Required of 16. Change any input above and every figure here is recalculated in your browser.

Inputs used

Pods to scheduleaccepts 1–100,000 pods
240 pods
CPU request per podaccepts 10–64,000 millicores
250 millicores
Memory request per podaccepts 16–262,144 MiB
512 MiB
vCPUs per nodeaccepts 1–128 vCPU
4 vCPU
Memory per nodeaccepts 1–2,048 GiB
16 GiB
Maximum pods per nodeaccepts 10–250 pods
30 pods
System pods per nodeaccepts 0–50 pods
6 pods
Node rateaccepts 0–100 USD/hour
0.192 USD/hour
Control plane rateaccepts 0–10 USD/hour
0 USD/hour

Results

Nodes Required
16 nodes
Allocatable CPU per Node
3.92 vCPU
Allocatable Memory per Node
12.67 GiB
Usable Pod Slots per Node
24 pods
Binding Constraint
CPU requests
Monthly Cost
$2,242.56

Step by step

  1. 1Values used
  2. 2Azure Kubernetes Service (AKS)
  3. 3Nodes Required= 16 nodes
  4. 4Allocatable CPU per Node= 3.92 vCPU
  5. 5Allocatable Memory per Node= 12.67 GiB
  6. 6Usable Pod Slots per Node= 24 pods
  7. 7Binding Constraint= CPU requests
  8. 8Monthly Cost= 2,242.56

Assumptions and limits

  • The result is derived only from the 9 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 Kubernetes Service (AKS) calculated?

nodes = max(pod CPU ÷ allocatable CPU, pod memory ÷ allocatable memory, pods ÷ usable slots), where allocatable memory subtracts 25%/20%/10%/6%/2% of successive memory bands plus a 750 MiB eviction threshold. AKS reserves node resources on a sliding scale — 25% of the first 4 GiB of memory, 20% of the next 4, 10% of the next 8, 6% of the next 112 and 2% beyond, plus a 750 MiB eviction threshold — so a 16 GiB node schedules roughly 12.5 GiB of pods. The node count is then the worst of three independent constraints: CPU requests, memory requests and the pods-per-node limit that Azure CNI defaults to 30.

Why does Azure Kubernetes Service (AKS) matter?

The pods-per-node limit is set at node-pool creation and cannot be changed afterwards, so a cluster sized only on CPU and memory can run out of IP-backed pod slots at a third of its capacity; the control plane itself is free on the Free tier, meaning almost the whole AKS bill is ordinary VM cost.

What values do I need to enter?

This calculator takes 9 inputs: Pods to schedule, CPU request per pod, Memory request per pod, vCPUs per node, Memory per node, Maximum pods per node, System pods per node, Node rate, Control plane rate. 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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