CIDR Subnet Calculator
Please enter a valid IPv4 address.
/32 (1 Host)
/31 (2 Hosts)
/30 (4 Hosts)
/29 (8 Hosts)
/28 (16 Hosts)
/27 (32 Hosts)
/26 (64 Hosts)
/25 (128 Hosts)
/24 (256 Hosts)
/23 (512 Hosts)
/22 (1024 Hosts)
/21 (2048 Hosts)
/20 (4096 Hosts)
/19 (8192 Hosts)
/18 (16384 Hosts)
/17 (32768 Hosts)
/16 (65536 Hosts)
/15 (131072 Hosts)
/14 (262144 Hosts)
/13 (524288 Hosts)
/12 (1048576 Hosts)
/11 (2097152 Hosts)
/10 (4194304 Hosts)
/9 (8388608 Hosts)
/8 (16777216 Hosts)
/7 (33554432 Hosts)
/6 (67108864 Hosts)
/5 (134217728 Hosts)
/4 (268435456 Hosts)
/3 (536870912 Hosts)
/2 (1073741824 Hosts)
/1 (2147483648 Hosts)
/0 (4294967296 Hosts)
Subnet Information
Network Address:
Broadcast Address:
Subnet Mask:
Wildcard Mask:
First Usable Host:
Last Usable Host:
Total Number of Hosts:
Usable Number of Hosts:
CIDR Notation:
Understanding CIDR and Subnetting
CIDR, which stands for Classless Inter-Domain Routing, is a method for allocating IP addresses and IP routing. It was introduced by the Internet Engineering Task Force in 1993 to replace the previous addressing architecture of Classful network design (Class A, B, and C networks).
How the CIDR Subnet Calculator Works
A subnet calculator takes an IP address and a netmask (CIDR prefix) and calculates the resulting network properties. This is essential for network administrators to determine how many devices can reside on a specific network and what the network boundaries are.
- Network Address: The first address in the range, identifying the network itself.
- Broadcast Address: The last address in the range, used to communicate with all hosts on the network.
- Usable Host Range: The IP addresses that can be assigned to devices like computers, printers, and routers.
- Subnet Mask: The dotted-decimal representation of the CIDR prefix (e.g., /24 is 255.255.255.0).
Common CIDR Examples
Here are some of the most common CIDR prefixes used in local and wide area networks:
| CIDR | Subnet Mask | Total Hosts |
|---|---|---|
| /30 | 255.255.255.252 | 4 |
| /24 | 255.255.255.0 | 256 |
| /16 | 255.255.0.0 | 65,536 |
| /8 | 255.0.0.0 | 16,777,216 |
Usable vs Total Hosts
In most standard IPv4 networking, the first address (Network) and the last address (Broadcast) cannot be assigned to hosts. Therefore, the number of usable hosts is typically (2 ^ host_bits) - 2. For example, in a /24 network, there are 256 total addresses, but only 254 are usable for actual devices.