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CIDR Calculator & Subnet Visualizer

Free online CIDR calculator. Compute network address, broadcast, subnet mask, host range, and total hosts from any CIDR notation.

Network Address
192.168.1.0
Broadcast Address
192.168.1.255
Subnet Mask
255.255.255.0
Wildcard Mask
0.0.0.255
First Usable Host
192.168.1.1
Last Usable Host
192.168.1.254
Total Usable Hosts
254
IP Class
C
IP (Binary)
11000000.10101000.00000001.00000000
Mask (Binary)
11111111.11111111.11111111.00000000

What Is a CIDR Calculator?

A CIDR (Classless Inter-Domain Routing) calculator breaks down a CIDR notation like 192.168.1.0/24 into its component parts: network address, broadcast address, subnet mask, usable host range, and total number of hosts. CIDR replaced the old classful addressing system and is the standard way to define IP address ranges in modern networking.

How to Use the CIDR Calculator

  1. Enter a CIDR notation in the input field (e.g., 192.168.1.0/24).
  2. The calculator instantly displays: network address, broadcast, subnet mask, wildcard mask, host range, host count, IP class, and binary representations.
  3. Click any copy button to copy a specific value to your clipboard.

Common Use Cases

  • VPC and Subnet Planning — Plan AWS VPC, Azure VNet, or GCP subnet layouts by calculating how many hosts each CIDR block can accommodate.
  • Firewall Rule Configuration — Verify that firewall allow/deny rules cover the intended IP ranges by checking network and broadcast boundaries.
  • Network Troubleshooting — Determine if two IP addresses are on the same subnet by comparing their network addresses.

FAQ

What does the /24 in CIDR notation mean?
The number after the slash is the prefix length — the number of bits used for the network portion. /24 means the first 24 bits are the network part, leaving 8 bits for host addresses, giving 254 usable hosts (2^8 - 2).
Why are there 2 fewer usable hosts than the total addresses?
In any subnet, the first address is the network address and the last is the broadcast address. Neither can be assigned to a host, so usable hosts = 2^(32-prefix) - 2. The exceptions are /31 (point-to-point links) and /32 (single host).
Does this support IPv6?
Currently this tool supports IPv4 CIDR notation only. IPv6 support may be added in the future.

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