GCP VPC Network Planner
Plan GCP subnets and GKE secondary ranges, allowing for the four reserved addresses and the per-node pod CIDR.
About GCP VPC Network Planner
GCP reserves four addresses per subnet rather than two, and GKE consumes addresses from two secondary ranges on top of the primary one. The per-node pod block is rounded up to a power of two of roughly double the pod limit, so 110 pods per node burns a full /24 — which is why a /14 pod range is the standard recommendation. Primary subnet ranges can be expanded but never shrunk, and a GKE secondary pod range cannot be changed after cluster creation, so an undersized range means rebuilding the cluster rather than editing a setting. Getting the arithmetic right once is far cheaper than renumbering later.
Formula
GCP VPC Network
usable = 2^(32 − prefix) − 4 reserved; each GKE node consumes 2^ceil(log2(pods per node × 2)) addresses from the secondary pod range, so nodes supported = pod range size ÷ that block.
- 4 reserved
- GCP reserves the network address, the default gateway, and the last two addresses in every subnet
- pod block per node
- Power-of-two CIDR GKE allocates per node — 110 pods rounds up to 256 addresses, a /24
- secondary range
- Alias IP range for pods or services, sized independently of the primary subnet
Worked example
With the default values below, GCP VPC Network Planner returns Usable Addresses in Subnet of 4,092. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Primary subnet prefixaccepts 8–29 bits
- 20 bits
- Secondary pod range prefixaccepts 8–28 bits
- 14 bits
- Secondary service range prefixaccepts 12–28 bits
- 20 bits
- Maximum pods per nodeaccepts 8–256 pods
- 110 pods
- Nodes planned in this subnetaccepts 1–100,000 nodes
- 200 nodes
- Other VMs and endpoints in the subnetaccepts 0–1,000,000 addresses
- 400 addresses
- Internal load balancer addressesaccepts 0–10,000 addresses
- 12 addresses
- Planned growth multipleaccepts 1–32 x
- 2 x
Results
- Usable Addresses in Subnet
- 4,092 addresses
- Reserved by Google
- 4 addresses
- Addresses Needed with Growth
- 1,224 addresses
- Primary Subnet Verdict
- Comfortable for the planned growth
- Pod Range Capacity
- 262,144 addresses
- Nodes the Pod Range Supports
- 1,024 nodes
- Addresses Carved per Node
- 256 addresses
- Service Range Capacity
- 4,096 services
Step by step
- 1Values used
- 2GCP VPC Network
- 3Usable Addresses in Subnet= 4,092 addresses
- 4Reserved by Google= 4 addresses
- 5Addresses Needed with Growth= 1,224 addresses
- 6Primary Subnet Verdict= Comfortable for the planned growth
- 7Pod Range Capacity= 262,144 addresses
- 8Nodes the Pod Range Supports= 1,024 nodes
Assumptions and limits
- The result is derived only from the 8 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 whole numbers, 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 GCP VPC Network calculated?
usable = 2^(32 − prefix) − 4 reserved; each GKE node consumes 2^ceil(log2(pods per node × 2)) addresses from the secondary pod range, so nodes supported = pod range size ÷ that block. GCP reserves four addresses per subnet rather than two, and GKE consumes addresses from two secondary ranges on top of the primary one. The per-node pod block is rounded up to a power of two of roughly double the pod limit, so 110 pods per node burns a full /24 — which is why a /14 pod range is the standard recommendation.
Why does GCP VPC Network matter?
Primary subnet ranges can be expanded but never shrunk, and a GKE secondary pod range cannot be changed after cluster creation, so an undersized range means rebuilding the cluster rather than editing a setting. Getting the arithmetic right once is far cheaper than renumbering later.
What values do I need to enter?
This calculator takes 8 inputs: Primary subnet prefix, Secondary pod range prefix, Secondary service range prefix, Maximum pods per node, Nodes planned in this subnet, Other VMs and endpoints in the subnet, Internal load balancer addresses, Planned growth multiple. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.
Why does 110 pods per node need 256 addresses?
GKE allocates a power-of-two CIDR per node and adds headroom so addresses are not reused immediately as pods churn. At the default limit of 110 that rounds up to 256 addresses — a /24 per node — which is the figure to multiply when sizing the pod range.