AWS VPC Subnet Planner

Design your VPC subnet architecture, visualize address space allocation, and export as Terraform, CLI, or Markdown

VPC Configuration

RFC 1918 range. AWS supports /16 to /28.
Used for subnet naming. Leave blank for a/b/c suffixes.

Subnet Sizing

Auto Calculate (recommended)
Reserve space for future expansion
Use contiguous blocks per tier
AWS Reserved IPs: AWS reserves 5 IPs per subnet (network address, VPC router, DNS server, future use, broadcast). A /24 subnet has 256 total IPs but only 251 usable.

AWS VPC Best Practices

This tool helps you plan your AWS VPC subnet architecture before deploying infrastructure. It handles CIDR math, alignment, and generates export-ready configurations.

  • Correct CIDR Alignment — all subnets are placed on proper bit boundaries
  • AWS Reserved IPs — accounts for the 5 IPs AWS reserves per subnet
  • Multi-AZ Layout — distributes subnets across 2 or 3 Availability Zones
  • Tier Separation — public, private, and custom tiers with clear naming
  • Visual Map — see how your address space is allocated at a glance
  • Export Ready — Terraform, AWS CLI, JSON, and Markdown output formats
NAT Gateway Note: If you have private subnets that need internet access, you will need a NAT Gateway in each public subnet (one per AZ for high availability). Each NAT Gateway requires an Elastic IP and incurs hourly + data transfer charges. For cost savings in non-production, consider a single NAT Gateway.
This calculator is for planning purposes only. Always validate your subnet design against your specific AWS account limits, service requirements, and organizational policies before deploying. For official documentation, see the AWS VPC User Guide.
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