How to Use Count in Terraform: Simple Guide with Examples

In Terraform, count is a meta-argument that lets you create multiple instances of a resource or module by specifying how many copies you want. You add count = number inside a resource block, and Terraform will create that many identical resources with indexes starting at zero.

Syntax

The count argument is placed inside a resource or module block. It accepts a number that tells Terraform how many copies of that resource to create. Each instance can be accessed using count.index, which starts at 0 and increments by 1 for each copy.

• count: Number of instances to create.
• count.index: The current instance number (0-based).

terraform

resource "aws_instance" "example" {
  count = 3

  ami           = "ami-12345678"
  instance_type = "t2.micro"

  tags = {
    Name = "example-${count.index}"
  }
}

Example

This example creates three AWS EC2 instances with unique names using count. Each instance gets a tag with its index number, so you can tell them apart.

terraform

provider "aws" {
  region = "us-east-1"
}

resource "aws_instance" "example" {
  count = 3

  ami           = "ami-0c55b159cbfafe1f0"
  instance_type = "t2.micro"

  tags = {
    Name = "example-instance-${count.index}"
  }
}

Output

Apply complete! Resources: 3 added, 0 changed, 0 destroyed.

Outputs:

aws_instance.example[0]: created
aws_instance.example[1]: created
aws_instance.example[2]: created

Common Pitfalls

Common mistakes when using count include:

• Using count with resources that do not support it.
• Not using count.index to differentiate instances, causing naming conflicts.
• Changing count values can cause resource replacement, so plan carefully.

Example of a wrong and right way to use count:

terraform

resource "aws_instance" "wrong" {
  count = 2

  ami           = "ami-12345678"
  instance_type = "t2.micro"

  tags = {
    Name = "duplicate-name"
  }
}

resource "aws_instance" "right" {
  count = 2

  ami           = "ami-12345678"
  instance_type = "t2.micro"

  tags = {
    Name = "unique-name-${count.index}"
  }
}

Quick Reference

Term	Description
count	Number of resource instances to create
count.index	Current instance index starting at 0
Use with care	Changing count can recreate resources
Works with	Most resource and module blocks
Common use	Create multiple similar resources easily

Key Takeaways

Use count to create multiple resource instances by specifying a number.

Access each instance with count.index to give unique names or settings.

Changing count can cause resource replacement; plan changes carefully.

Not all resources support count, so check documentation before use.

Use count to simplify and reduce repeated code in Terraform configurations.