AWS - Free tool

AWS Transit Gateway cost calculator

Model the hub-and-spoke tax on multi-VPC AWS. Enter attachments, monthly data processed, and cross-AZ traffic to see the TGW bill plus the EC2 data transfer line that often gets missed.

Estimated monthly TGW bill

$0 per year

Attachment cost	$0	15 attachments x 730 hours x $0.050/hr
Data-processing cost	$0	20,000 GB x $0.020/GB
Cross-AZ surcharge	$0	40% of 20,000 GB x $0.01/GB

Check these first when TGW cost is high: unused VPC attachments, S3 and DynamoDB routes crossing TGW instead of Gateway Endpoints, chatty app and database VPCs, inspection paths that cross the TGW twice, and bulk cross-region transfers.

Why TGW bills surprise teams

Transit Gateway looks small on the pricing page: attachment hours plus data processed. In real accounts, the total grows when workloads send AWS-native traffic through the hub, inspection paths cross the TGW twice, and cross-AZ transfer lands on a different bill line.

A 15-attachment hub with 20 TB of monthly traffic and 40 percent cross-AZ runs just over $1,000 per month at the default US rates. The fix is usually route cleanup, Gateway Endpoints, and direct peering for the busiest VPC pairs.

Frequently asked

Why is Transit Gateway often more expensive than teams expect?

Every attachment bills per hour even when traffic is low. The per-GB processing charge applies to bytes crossing the TGW. Cross-AZ charges do not appear on the TGW line at all; they show under EC2 data transfer.
What is the typical regional rate?

US and EU regions are commonly around $0.05 per attachment hour and $0.02 per GB processed. Asia-Pacific regions are often slightly higher. Override the defaults if your private pricing is different.
Should I use Transit Gateway or VPC peering?

VPC peering is cheaper for a small number of stable VPC pairs. Transit Gateway is cleaner when many VPCs need shared routing, inspection, or cross-account connectivity. The cost check is traffic volume plus route-table complexity.
How do I reduce Transit Gateway cost?

Start with unused attachments, S3 and DynamoDB routes that should use Gateway Endpoints, chatty app and database VPCs that should be peered, inspection paths that cross the TGW twice, and bulk cross-region transfers.