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VPC Peering Calculator

Count the peering connections, route entries and cross-region transfer cost of a VPC mesh, and test the per-VPC quota.

About VPC Peering Calculator

VPC peering is not transitive: traffic cannot hop through a peered VPC to reach a third one, so any-to-any connectivity requires a full mesh of n(n − 1) ÷ 2 connections. The route table burden grows with it, because every VPC needs an explicit route to every peer, and peering has no hourly charge — you pay only for data transfer, which is free within an Availability Zone and charged per GB across regions. The quadratic growth is the whole argument for a Transit Gateway: eight VPCs need 28 peerings and 56 route entries, while twenty need 190 peerings that no team can audit by hand.

Formula

VPC Peering

full mesh connections = n(n − 1) ÷ 2; each VPC terminates n − 1 peerings and needs n − 1 route entries.

n
Number of VPCs being interconnected
n − 1
Peerings and routes each VPC must carry
quota
Active peering connections allowed per VPC

Worked example

With the default values below, VPC Peering Calculator returns Peering Connections in a Full Mesh of 28. Change any input above and every figure here is recalculated in your browser.

Inputs used

VPCs to interconnectaccepts 2–200 VPCs
8 VPCs
Active peerings per VPC quotaaccepts 1–125 connections
50 connections
Cross-region data transfer per monthminimum 0 GB
500 GB
Price per GB transferred cross-regionaccepts 0–2 USD
0.02 USD

Results

Peering Connections in a Full Mesh
28
Peerings Terminating on Each VPC
7
Route Entries Added per VPC
7
Monthly Cross-region Transfer Cost
$10.00
Peering Quota Check
Within the 50 active peerings per VPC quota

Step by step

  1. 1Values used
  2. 2VPC Peering
  3. 3Peering Connections in a Full Mesh= 28
  4. 4Peerings Terminating on Each VPC= 7
  5. 5Route Entries Added per VPC= 7
  6. 6Monthly Cross-region Transfer Cost= 10.00
  7. 7Peering Quota Check= Within the 50 active peerings per VPC quota

Assumptions and limits

  • The result is derived only from the 4 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 2 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

How is VPC Peering calculated?

full mesh connections = n(n − 1) ÷ 2; each VPC terminates n − 1 peerings and needs n − 1 route entries. VPC peering is not transitive: traffic cannot hop through a peered VPC to reach a third one, so any-to-any connectivity requires a full mesh of n(n − 1) ÷ 2 connections. The route table burden grows with it, because every VPC needs an explicit route to every peer, and peering has no hourly charge — you pay only for data transfer, which is free within an Availability Zone and charged per GB across regions.

Why does VPC Peering matter?

The quadratic growth is the whole argument for a Transit Gateway: eight VPCs need 28 peerings and 56 route entries, while twenty need 190 peerings that no team can audit by hand.

What values do I need to enter?

This calculator takes 4 inputs: VPCs to interconnect, Active peerings per VPC quota, Cross-region data transfer per month, Price per GB transferred cross-region. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.

When should I switch from peering to a Transit Gateway?

Once the mesh passes roughly five to ten VPCs, or as soon as you need transitive routing, shared VPN and Direct Connect, or centralised inspection. Peering stays attractive for a small number of high-bandwidth pairs because it has no hourly or data processing charge.

Does peering cost anything when idle?

No. A peering connection has no hourly charge. You pay only for data transfer, and traffic between Availability Zones or regions is charged at the standard rates — confirm the current per-GB figures for your regions with AWS.

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