Cidr Calc

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

1. 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.
2. 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
3. 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
4. Determine private vs public:
   • Private: 10.x.x.x, 172.16–31.x.x, 192.168.x.x, 127.x.x.x (loopback)
5. Compute binary as four 8-bit groups joined by dots.
6. 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:

text

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:          11000000.10101000.00000001.00000000

Input: 10.0.0.0/8

Output:

text

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:          00001010.00000000.00000000.00000000

Error 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.