google_compute_subnetwork cost estimation

A google_compute_subnetwork is the regional slice of a VPC where VMs and other resources get their internal IP addresses. Creating a subnetwork is free. Assigning primary and secondary CIDR ranges is free, and so is enabling Private Google Access on it. There is no per-subnet or per-IP-range charge.

Cost is driven by what you put in the subnet and where its traffic goes. VMs in the subnet carry their own compute and disk cost. Traffic between subnets in different zones bills per GB, traffic to other regions bills per GB, and internet egress from instances in the subnet is tiered per GB. Secondary ranges used for GKE Pods and Services are free to define, but the workloads that consume them are not.

One subnet feature has a genuine cost lever attached: enabling Private Google Access lets private VMs reach Google APIs without routing through a Cloud NAT gateway, which avoids NAT data-processing charges. c3x prices the VMs, NAT, and egress associated with a subnet and treats the subnet and its IP ranges as the free addressing layer they are.

Terraform example

A minimal but realistic configuration that C3X can estimate.

resource "google_compute_subnetwork" "app" {
  name                     = "app-subnet"
  ip_cidr_range            = "10.0.1.0/24"
  region                   = "us-central1"
  network                  = google_compute_network.main.id
  private_ip_google_access = true

  secondary_ip_range {
    range_name    = "pods"
    ip_cidr_range = "10.4.0.0/14"
  }
}

Pricing dimensions

What you actually pay for when you provision google_compute_subnetwork.

Dimension	Unit	What's being charged
Subnetwork and IP ranges	free	The subnet, its primary and secondary CIDR ranges, and Private Google Access have no charge. $0
Inter-zone and inter-region egress	per GB	Traffic from resources in the subnet to other zones or regions. Inter-zone: $0.01/GB
Internet egress	per GB	Bytes leaving the subnet's instances to the public internet, tiered by destination after the free tier. ~$0.12/GB (Premium tier)

Optimization tips

Common ways to reduce google_compute_subnetwork cost without changing the workload.

Enable Private Google Access

Removes NAT processing on Google API traffic

Turning on private_ip_google_access lets private VMs reach Google APIs directly, bypassing Cloud NAT and removing NAT data-processing charges on that traffic.

Colocate chatty workloads in one region

Traffic between subnets in different regions bills per GB. Keeping services that talk to each other in the same region avoids inter-region egress.

Size secondary ranges for GKE deliberately

Secondary ranges are free but hard to change later. Plan Pod and Service ranges up front to avoid rebuilding a cluster, which is operationally expensive.

FAQ

Does a GCP subnetwork cost money?

No. The subnetwork, its primary and secondary IP ranges, and Private Google Access are free. Cost comes from the resources you place in it and the traffic they generate.

Is there a charge for reserving IP ranges in a subnet?

No. Defining CIDR ranges, including secondary ranges for GKE Pods and Services, is free. Static external IP addresses are a separate resource with their own charge.

How does a subnet affect my bill?

Indirectly, through the VMs in it and the traffic they send. Inter-zone and inter-region transfer and internet egress bill per GB. Enabling Private Google Access can cut Cloud NAT costs.