IP Browser Tools

NETWORK TOOL

CIDR Calculator

Analyze IP addresses and subnet masks. Calculate network details, host counts, usable ranges, and binary representations for IPv4 and IPv6 networks.

IP Version:
Prefix Length: /24
CIDR Range 192.168.1.0/24
Subnet Netmask 255.255.255.0
Usable Host IP Range 192.168.1.1 - 192.168.1.254

Network Subnet Details

Network Address 192.168.1.0
Broadcast Address 192.168.1.255
Wildcard Mask 0.0.0.255
Total Host IPs 256
Usable Host IPs 254

Binary Representation

IP Address (Binary) 
11000000.10101000.00000001.00000001
Subnet Netmask (Binary) 
11111111.11111111.11111111.00000000
Network ID (Binary) 
11000000.10101000.00000001.00000000

Subnet Divisions (Splits)

Split this range into smaller subnets.

Audit & Export Data

Export these subnet parameters for network configurations or scripts.

Understanding CIDR & Subnetting

IP subnetting is a core pillar of modern networking, enabling administrators to divide larger blocks of IP addresses into smaller, separate subnetworks. This process controls broadcast domains, secures traffic, and optimizes network routing paths.

What is CIDR?

Historically, IP addresses were divided into strict classes (Class A, Class B, Class C) that allocated set block sizes. This was highly inefficient: a business requiring 300 IP addresses was forced to lease a Class B block containing over 65,000 addresses, wasting the remainder.

Classless Inter-Domain Routing (CIDR) solves this by allowing subnet mask boundaries to reside at any bit position rather than octet boundaries. CIDR uses a compact slash notation like 192.168.1.0/24, where the number after the slash indicates how many bits are dedicated to the network prefix.

Calculating a Subnet

To calculate the size of an IPv4 subnet from its CIDR prefix:

  • Total Hosts: Calculated as 2^(32 - Prefix). For `/24`, it is 2^(32 - 24) = 256.
  • Usable Hosts: In most subnets, the first address is reserved as the Network IP, and the last address is reserved as the Broadcast IP. Thus, usable hosts are Total - 2.
  • Wildcard Mask: This mask is the bitwise inverse of the netmask. For netmask 255.255.255.0, the wildcard is 0.0.0.255.

IPv6 Subnetting

IPv6 expands the address space to 128 bits. The notation is similar to IPv4, but the prefix is typically much larger (standard residential allocations are `/48` or `/56`, while individual subnets inside networks are almost always `/64`). Because IPv6 has a massive address space, broadcast addresses do not exist; instead, multicast and anycast routing are used.

Frequently Asked Questions

What does CIDR stand for?
CIDR stands for Classless Inter-Domain Routing. It was introduced in 1993 to replace the older class-based IP routing system (Class A, B, and C networks). CIDR allows for more flexible allocation of IP addresses, reducing waste by defining subnets of any size using a slash notation (e.g., /24, /27).
How does a CIDR calculator work?
A CIDR calculator parses an IP address and a prefix length (the number after the slash). It converts the IP address into its binary representation and applies a subnet mask to calculate key network parameters, including the network address, wildcard mask, broadcast address, range of usable IP addresses, and total number of host IPs.
What is a /24 subnet mask?
A /24 prefix indicates that the first 24 bits of the 32-bit IP address represent the network portion, leaving 8 bits for host addresses. In decimal format, a /24 subnet mask is 255.255.255.0. It provides a total of 256 IP addresses, of which 254 are usable for hosts (excluding the network and broadcast addresses).
Does this tool support IPv6 CIDR calculations?
Yes, our CIDR calculator fully supports both IPv4 (32-bit addresses) and IPv6 (128-bit addresses). For IPv6, it calculates the network prefix, the host range, and the total block size (which can be massive, e.g., 2^64 for a standard /64 subnet).