aws_internet_gateway cost estimation

An aws_internet_gateway (IGW) is the component that lets resources in a public subnet reach the internet and be reached from it. There is no charge for the gateway, for attaching it to a VPC, or for the number of gateways (one per VPC). Unlike a NAT Gateway, an internet gateway has no hourly fee and no per-GB processing fee of its own.

What it enables does cost money: data transfer out to the internet. Traffic leaving AWS through an internet gateway is billed at standard egress rates, roughly $0.09/GB for the first tier from most regions, with the first 100 GB per month free across the account. Inbound data transfer from the internet is free. So an internet gateway fronting a busy public service can anchor a meaningful egress bill even though the gateway line item is zero.

Because the IGW itself is free, the optimization question is about the egress it carries: fronting heavy download traffic with CloudFront can cut per-GB cost and offload origin transfer, and keeping large data flows internal (S3 gateway endpoints, same-region architecture) avoids internet egress entirely. c3x prices the internet data transfer out that flows through the gateway and treats the gateway as the free component it is.

Terraform example

A minimal but realistic configuration that C3X can estimate.

resource "aws_internet_gateway" "main" {
  vpc_id = aws_vpc.main.id

  tags = {
    Name = "main"
  }
}

Pricing dimensions

What you actually pay for when you provision aws_internet_gateway.

Dimension	Unit	What's being charged
Internet gateway	free	The gateway, its VPC attachment, and routing have no charge. $0
Data transfer out to internet	per GB	Outbound traffic to the internet through the gateway is billed at standard egress rates. ~$0.09/GB (first 100 GB/mo free)
Data transfer in	free	Inbound traffic from the internet is not charged. $0

Optimization tips

Common ways to reduce aws_internet_gateway cost without changing the workload.

Front heavy egress with CloudFront

Lower per-GB rate on cached content

Serving downloads or media through CloudFront lowers the per-GB rate versus direct internet-gateway egress and offloads repeat traffic to the cache.

Use S3 gateway endpoints for internal data flows

Avoids internet egress on that traffic

Keep large S3 transfers inside AWS with a free gateway endpoint instead of routing them out through the internet gateway.

Stay in-region for service-to-service traffic

Internet egress applies when traffic leaves AWS. Same-region, private-network architectures avoid the gateway path entirely.

FAQ

Does an AWS internet gateway cost money?

No. The internet gateway itself is completely free, with no hourly or per-GB charge, unlike a NAT Gateway. You pay only for the data transfer out to the internet that flows through it.

What is the difference in cost between an internet gateway and a NAT Gateway?

An internet gateway is free and carries only standard egress transfer cost. A NAT Gateway adds about $0.045/hour plus $0.045/GB processed on top of that egress. Public subnets use the free IGW; private subnets pay for the NAT Gateway.

How do I reduce internet gateway costs?

Reduce internet egress: front download-heavy traffic with CloudFront, keep large data flows inside AWS with S3 gateway endpoints, and prefer same-region architectures. The gateway is free, so all savings come from the transfer it carries.