How to Use AWS Subnet Calculator

A step-by-step guide to planning your AWS VPC network

Step 1: Define Your VPC

Start by entering your VPC CIDR block. This is the overall IP address range for your Virtual Private Cloud. Common choices include 10.0.0.0/16, 172.16.0.0/16, or 192.168.0.0/16.

Example: Enter 10.0.0.0/16 in the VPC CIDR field. This provides 65,536 IP addresses for your VPC.

Step 2: Select AWS Region

Choose the AWS region where your VPC will be deployed. This determines the available Availability Zones for your subnets.

Example: Select "us-east-1" (N. Virginia) to access up to 6 Availability Zones.

Step 3: Plan Your Subnets

Add subnets for different purposes (public, private, database) across multiple Availability Zones. For each subnet, specify:

  • Subnet name (e.g., Public-AZ1, Private-AZ2)
  • Subnet type (Public or Private)
  • Availability Zone
  • CIDR block or subnet mask

Example: Create a public subnet with CIDR 10.0.0.0/24 in AZ1, a private subnet with CIDR 10.0.1.0/24 in AZ1, and a database subnet with CIDR 10.0.2.0/24 in AZ1.

Step 4: Visualize Your Network

Use the network topology visualization to see how your subnets are organized within your VPC. This helps you understand the relationship between subnets and identify any potential issues.

Step 5: Export Your Configuration

Once you're satisfied with your subnet design, you can export it in various formats:

  • JSON for documentation
  • CSV for spreadsheet analysis
  • Terraform code for infrastructure as code
  • CloudFormation template for AWS deployment

Best Practices

  • Plan for future growth by allocating larger CIDR blocks than currently needed.

  • Use consistent subnet sizes across Availability Zones for the same tier.

  • Deploy resources across multiple Availability Zones for high availability.

  • Reserve the first few and last few IP addresses in each subnet for AWS services.

Ready to start planning your AWS VPC network?