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CIDR Calculator

Network Information
Network Address
Broadcast Address
Subnet Mask
Wildcard Mask
First Usable Host
Last Usable Host
Total Addresses
Usable Hosts
Prefix Length
IP Class
Private Range

How to Use

Enter an IPv4 address in CIDR notation (e.g., 192.168.1.0/24). The tool instantly calculates network address, broadcast address, subnet mask, wildcard mask, host range, and total number of usable hosts.

CIDR Notation

CIDR (Classless Inter-Domain Routing) notation combines an IP address with a prefix length separated by a slash. The prefix (0-32) indicates how many bits define the network portion. /24 means the first 24 bits are the network (256 addresses), /16 means 65,536 addresses, and /32 is a single host. CIDR replaced the older classful addressing system.

Use Cases

  • VPC/subnet design: calculate IP ranges and host counts when splitting subnets in AWS VPC or GCP VPC
  • Firewall rules: determine the exact CIDR range to allow or deny in security groups or iptables rules
  • Network troubleshooting: verify whether a target IP falls within the same subnet during connectivity issues
  • IP address planning: choose the right prefix length for the number of hosts needed per office or site

Common CIDR Prefixes

  • /32 = 1 address: single host — used in firewall rules to allow or block a specific IP
  • /28 = 16 addresses (14 usable): small subnet — the minimum recommended VPC subnet size in AWS
  • /24 = 256 addresses (254 usable): the most common subnet — ideal for office LANs and small server pools
  • /16 = 65,536 addresses: large network — the default AWS VPC CIDR (e.g., 10.0.0.0/16)
  • /8 = ~16.7 million addresses: very large network — 10.0.0.0/8 covers the entire Class A private space

Privacy

All calculations happen entirely in your browser. No IP addresses or network data is sent to a server, stored, or logged.