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Route Table Calculator

Count the route tables, routes and subnet associations a VPC design needs and check them against the AWS route quota.

About Route Table Calculator

A subnet associates with exactly one route table, so the table count is the number of distinct routing behaviours multiplied by the zones you replicate them in — a per-zone private table is required whenever each zone routes to its own NAT Gateway. Each table starts with one automatic local route per associated VPC CIDR block, and the default quota of 50 routes counts static entries but not propagated Transit Gateway routes. Route tables are the least visible AWS quota: hitting 50 routes mid-migration means either an emergency aggregation exercise or a support ticket on the critical path.

Formula

Route Table

tables = routing behaviours × zones; routes per table = local routes (one per VPC CIDR block) + 1 default route + static routes.

routing behaviours
Groups of subnets that need different next hops
local routes
Automatic routes for each associated VPC CIDR block
quota
Routes allowed per route table

Worked example

With the default values below, Route Table Calculator returns Route Tables Needed of 9. Change any input above and every figure here is recalculated in your browser.

Inputs used

Subnets in the VPCaccepts 1–400 subnets
12 subnets
Distinct routing behavioursaccepts 1–50 tiers
3 tiers
Availability Zones in useaccepts 1–6 zones
3 zones
CIDR blocks associated with the VPCaccepts 1–5 blocks
2 blocks
Static routes per tableaccepts 0–200 routes
14 routes
Routes per route table quotaaccepts 10–1,000 routes
50 routes

Results

Route Tables Needed
9
Routes per Table
17
Subnet Associations
12
Route Quota Headroom
66.0%
Quota Check
Within quota with 33 routes spare per table

Step by step

  1. 1Values used
  2. 2Route Table
  3. 3Route Tables Needed= 9
  4. 4Routes per Table= 17
  5. 5Subnet Associations= 12
  6. 6Route Quota Headroom= 66.0
  7. 7Quota Check= Within quota with 33 routes spare per table

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 1 decimal place, 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 Route Table calculated?

tables = routing behaviours × zones; routes per table = local routes (one per VPC CIDR block) + 1 default route + static routes. A subnet associates with exactly one route table, so the table count is the number of distinct routing behaviours multiplied by the zones you replicate them in — a per-zone private table is required whenever each zone routes to its own NAT Gateway. Each table starts with one automatic local route per associated VPC CIDR block, and the default quota of 50 routes counts static entries but not propagated Transit Gateway routes.

Why does Route Table matter?

Route tables are the least visible AWS quota: hitting 50 routes mid-migration means either an emergency aggregation exercise or a support ticket on the critical path.

What values do I need to enter?

This calculator takes 6 inputs: Subnets in the VPC, Distinct routing behaviours, Availability Zones in use, CIDR blocks associated with the VPC, Static routes per table, Routes per route table quota. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.

Do propagated Transit Gateway routes count against the quota?

No. The default limit of 50 applies to static routes per route table; dynamically propagated routes from a Transit Gateway association are counted separately, which is one reason a hub design scales further than a peering mesh full of static entries.

Why do I need one private route table per Availability Zone?

Because the next hop differs. If each zone has its own NAT Gateway for resilience and to avoid cross-zone charges, each zone's private subnets need a table whose default route points at the local gateway.

Related Calculators

Route Table Calculator – Calculate Route Tables Needed