CIDR Calculator

Calculate IP ranges and subnet details from CIDR notation.

Network Summary
192.168.1.0/24
Class C · Private · 254 usable hosts
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 Class C
Address Type Private (RFC 1918)
Binary Representation
Network 11000000 10101000 00000001 00000000
Mask 11111111 11111111 11111111 00000000

Frequently Asked Questions

What is CIDR notation?

CIDR (Classless Inter-Domain Routing) notation combines an IP address with a prefix length: 192.168.1.0/24 means the first 24 bits are the network portion. The prefix length (after the slash) determines network size. /24 = 256 addresses, /16 = 65,536 addresses, /8 = 16,777,216 addresses. Smaller prefix = larger network.

How do I find the IP range from a CIDR block?

The calculator computes the network address (first address, all host bits 0), broadcast address (last address, all host bits 1), and the usable IP range (everything in between). For 192.168.1.0/24: network = 192.168.1.0, first usable = 192.168.1.1, last usable = 192.168.1.254, broadcast = 192.168.1.255.

What is the difference between subnet mask and prefix length?

They represent the same information differently. /24 = 255.255.255.0 (24 ones followed by 8 zeros in binary). /16 = 255.255.0.0. /32 = 255.255.255.255 (single host). The calculator shows both the CIDR prefix length and the equivalent dotted-decimal subnet mask for any entry.

How many usable hosts does a CIDR block have?

Usable hosts = 2^(32 - prefix) - 2. The subtraction removes the network and broadcast addresses. /24 = 254 hosts, /25 = 126, /26 = 62, /27 = 30, /28 = 14, /29 = 6, /30 = 2, /31 = 2 (point-to-point), /32 = 1 (single host). The calculator shows total addresses and usable hosts.

Does the calculator support IPv6?

Yes — enter an IPv6 CIDR block (e.g., 2001:db8::/32) and the calculator shows the full network range, prefix length, and number of addresses. IPv6 addresses are 128 bits, so a /64 prefix provides 2^64 (18.4 quintillion) addresses for a single subnet — far more than IPv4.