- name
- cidr-calc
- description
- Calculate subnet information from CIDR notation. Use when the user asks to calculate a subnet, find the network address, broadcast address, host range, subnet mask, or number of hosts for an IP in CIDR notation like 192.168.1.0/24.
CIDR Calculator
Given an IP address in CIDR notation, compute all subnet parameters: network address, broadcast, host range, subnet mask, wildcard mask, host counts, IP class, and binary representation.
Input
- A CIDR notation string in the format
A.B.C.D/N(e.g.192.168.1.0/24)
Output
A structured result with these fields:
- CIDR Notation (normalized)
- Network Address
- Broadcast Address
- Subnet Mask
- Wildcard Mask
- First Usable Host
- Last Usable Host
- Total Hosts (2^(32-N))
- Usable Hosts
- IP Class (A / B / C / D Multicast / E Reserved)
- Network Type (Private / Public)
- Binary Representation of the IP
Instructions
- Validate the input. It must match
\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}\/\d{1,2}. Each octet must be 0–255. Prefix must be 0–32. - Compute values using standard subnet math:
- maskNum = (0xFFFFFFFF << (32 - prefix)) >>> 0 - wildcardNum = ~maskNum >>> 0 - networkNum = (ipNum & maskNum) >>> 0 - broadcastNum = (networkNum | wildcardNum) >>> 0 - totalHosts = 2^(32 - prefix) - usableHosts: if prefix == 32 → 1; if prefix == 31 → 2; else totalHosts - 2
- Determine IP class from first octet:
- 1–126 → A; 128–191 → B; 192–223 → C; 224–239 → D (Multicast); 240–255 → E (Reserved); 127 → Loopback
- Determine private vs public:
- Private: 10.x.x.x, 172.16–31.x.x, 192.168.x.x, 127.x.x.x (loopback)
- Compute binary as four 8-bit groups joined by dots.
- Present results in a clear labeled format.
Quick CIDR reference
| CIDR | Subnet Mask | Total Hosts |
|---|---|---|
| /8 | 255.0.0.0 | 16,777,216 |
| /16 | 255.255.0.0 | 65,536 |
| /20 | 255.255.240.0 | 4,096 |
| /22 | 255.255.252.0 | 1,024 |
| /24 | 255.255.255.0 | 256 |
| /28 | 255.255.255.240 | 16 |
| /30 | 255.255.255.252 | 4 |
| /32 | 255.255.255.255 | 1 |
Options
- Input is always a single CIDR string; no additional options.
Examples
Input: 192.168.1.0/24
Output:
CIDR Notation: 192.168.1.0/24
Network Address: 192.168.1.0
Broadcast: 192.168.1.255
Subnet Mask: 255.255.255.0
Wildcard Mask: 0.0.0.255
First Host: 192.168.1.1
Last Host: 192.168.1.254
Total Hosts: 256
Usable Hosts: 254
IP Class: C
Network Type: Private
Binary: 11000000.10101000.00000001.00000000Input: 10.0.0.0/8
Output:
CIDR Notation: 10.0.0.0/8
Network Address: 10.0.0.0
Broadcast: 10.255.255.255
Subnet Mask: 255.0.0.0
Wildcard Mask: 0.255.255.255
First Host: 10.0.0.1
Last Host: 10.255.255.254
Total Hosts: 16,777,216
Usable Hosts: 16,777,214
IP Class: A
Network Type: Private
Binary: 00001010.00000000.00000000.00000000Error Handling
- If the input is not valid CIDR notation, say so and provide the expected format (
A.B.C.D/N). - If an octet exceeds 255 or the prefix exceeds 32, explain the validation error.
- If the user provides an IP without a prefix (e.g.
192.168.1.1), ask for the prefix length or assume /32.