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Subnet Calculator

Calculate network address, broadcast, usable IP range, and host count from IP address and CIDR prefix. Supports IPv4 and IPv6.

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How to Use

Expand how to use
  1. 1

    Enter CIDR Notation

    Enter the IP address and prefix length in CIDR notation (e.g., 192.168.1.0/24, 2001:db8::/32).

  2. 2

    View Results

    Network address, broadcast address, usable IP range, host count, and more are calculated automatically.

  3. 3

    Copy Values

    Click the copy button next to each result to copy the value to your clipboard.

Enter a CIDR notation (e.g., 192.168.1.0/24) to calculate

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About Subnet Calculator

The Subnet Calculator computes subnet information from an IP address and CIDR prefix. Instantly get network address, broadcast address, usable IP range, host count, subnet mask, and wildcard mask. Essential for designing AWS VPC subnets, writing firewall ACLs, and planning VLAN segmentation. Supports both IPv4 and IPv6.

Key Features

  • Subnet calculation supporting both IPv4 and IPv6
  • Instant calculation of network address, broadcast, and usable IP range
  • Display of subnet mask, wildcard mask, and IP class
  • One-click copy for each result value
  • Simple operation — just enter CIDR notation

Use Cases

  • Design AWS VPC or Azure VNet subnets with the correct CIDR blocks
  • Calculate usable host ranges when provisioning cloud infrastructure
  • Write IP range rules for security groups, ACLs, or iptables
  • Plan VLAN segmentation for office or data center networks
  • Study for CompTIA Network+, CCNA, or other networking certifications

Frequently Asked Questions

What is CIDR?

CIDR (Classless Inter-Domain Routing) is a notation method that separates an IP address and its network prefix length with a slash. For example, "192.168.1.0/24" indicates that the first 24 bits are the network portion.

What is the difference between IPv4 and IPv6?

IPv4 uses 32-bit addresses (e.g., 192.168.1.0), while IPv6 uses 128-bit addresses (e.g., 2001:db8::). IPv6 was designed to address the exhaustion of IPv4 addresses.

What CIDR block should I use for an AWS VPC?

AWS recommends using a /16 block (up to 65,536 addresses) for your VPC to allow room for growth, then dividing it into smaller subnets (/24 gives 254 usable hosts). Common VPC ranges are 10.0.0.0/16 or 172.16.0.0/16 from the RFC 1918 private address space.

What is the difference between a subnet mask and a wildcard mask?

A subnet mask represents the network portion with 1s and the host portion with 0s (e.g., 255.255.255.0). A wildcard mask is the inverse, representing the host portion with 1s (e.g., 0.0.0.255). Wildcard masks are primarily used in ACL (Access Control List) configurations.

What are the private IP address ranges?

Private IP addresses defined in RFC 1918 include three ranges: 10.0.0.0/8 (Class A), 172.16.0.0/12 (Class B), and 192.168.0.0/16 (Class C). These can be freely used within internal networks and home LANs.