Transit Gateway Planner
Plan transit gateway attachments, routing and bandwidth across connected VPCs.
About Transit Gateway Planner
Transit gateway planning spans three dimensions: cost (a flat hourly fee per attachment plus a usage-based fee for data actually processed — cost = attachments × $/hr × hours + data_processed_GB × $/GB), route capacity (each attachment contributes routes to a shared route table with a practical ceiling, commonly cited around 10,000 routes), and bandwidth (aggregate throughput divided across attachments, each with its own burst ceiling).
Formula
Total monthly cost
cost = attachments × price_per_hr × hours_per_month + data_processed_GB × price_per_GB
- n
- Number of attachments
- p_a
- Hourly price per attachment
- h
- Hours per month (approximately 730)
- D
- Data processed in GB
- p_d
- Price per GB processed
Worked example
With the default values below, Transit Gateway Planner returns Estimated Total Monthly Cost of $10,365.00. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Number of Attachmentsaccepts 1–5,000
- 10
- Price per Attachment (hourly)minimum 0
- 0.05
- Data Processed per Monthminimum 0 GB
- 500,000 GB
- Data Processing Price per GBminimum 0
- 0.02
- Average Routes per Attachmentminimum 1
- 20
- Aggregate Bandwidth Neededminimum 0.1 Gbps
- 50 Gbps
Results
- Estimated Total Monthly Cost
- $10,365.00
- Attachment Cost
- $365.00
- Data Processing Cost
- $10,000.00
- Total Routes (across all attachments)
- 200
- Route Table Utilization (vs. 10,000 typical limit)
- 2.00%
- Avg. Bandwidth per Attachment
- 5.000 Gbps
Step by step
- 1Values used
- 2Total monthly cost
- 3Estimated Total Monthly Cost= 10,365.00
- 4Attachment Cost= 365.00
- 5Data Processing Cost= 10,000.00
- 6Total Routes (across all attachments)= 200
- 7Route Table Utilization (vs. 10,000 typical limit)= 2.00
- 8Avg. Bandwidth per Attachment= 5.000 Gbps
Assumptions and limits
- The result is derived only from the 6 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
- Figures are rounded for display to 3 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
Why does a transit gateway have a route limit?
Route tables are held in memory on the gateway's control plane and propagated to every attachment, so there's a practical ceiling (commonly around 10,000 routes per route table on major cloud platforms) to keep propagation and lookup performant at scale — large deployments should plan for route summarization rather than one route per fine-grained subnet.
How is transit gateway cost typically structured?
Most cloud providers charge a flat hourly fee per attachment (VPC, VPN, or Direct Connect/ExpressRoute) plus a separate per-GB fee for data actually processed through the gateway — cost scales with both how many things you connect and how much traffic flows between them.
When should I use route summarization?
When total routes across attachments approach the route table's practical limit, summarizing many small routes into fewer, larger aggregate routes (where addressing hierarchy allows) reduces route table pressure and keeps the gateway comfortably under its capacity ceiling.