calculateCIDR

Fast CIDR network calculator for the terminal: IPv4 & IPv6, subnet division, address classification, binary view and JSON output for scripts.

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✨ Features

• 🌐 IPv4 & IPv6 — network ID, host range, broadcast, netmask, wildcard and host count
• 🎯 Any address works — 10.1.2.3/20 shows the address and the network it belongs to
• 🧩 Subnet division — split any network into N subnets with correct prefix math
• 🏷️ Address type — Private (RFC 1918), Public, CGNAT, Loopback, Link-local, Multicast, Documentation…
• 📐 RFC 3021 aware — /31 point-to-point links have 2 usable hosts, /32 has 1
• 🔠 Binary display — every IPv4 field in binary octets
• 🤖 JSON output — pipe results into jq, Ansible or your own scripts
• 🔇 Script-friendly — plain output when piped or when NO_COLOR is set; errors go to stderr

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📥 Installation

pip install cidr-calculator

Or from source:

git clone https://github.com/serber-info/calculateCIDR.git
cd calculateCIDR
pip install -e .

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🛠 Usage

cidr IP/PREFIX [-divide N] [-binary] [--json]

Option	Description
IP/PREFIX	Address with CIDR prefix (-ip IP/PREFIX also works)
-divide N	Split the network into N subnets
-binary	Show IPv4 addresses in binary
-j, --json	Machine-readable JSON output
-v, --version	Show version
-h, --help	Show help

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🎨 Examples

Network details

cidr 192.168.1.10/24

  ╔══════════════════════════════════════════════╗
  ║ 192.168.1.0/24  ·  IPv4                      ║
  ╚══════════════════════════════════════════════╝

  Address     192.168.1.10
  Network ID  192.168.1.0
  First Host  192.168.1.1
  Last Host   192.168.1.254
  Broadcast   192.168.1.255
  Netmask     255.255.255.0
  Wildcard    0.0.0.255
  Prefix      /24
  Hosts       254
  Type        Private (RFC 1918)

Subnet division

cidr 192.168.1.0/24 -divide 4

  ╔════════════════════════════════════════════════════╗
  ║ 192.168.1.0/24  ·  4 subnets  /  new prefix /26    ║
  ╚════════════════════════════════════════════════════╝

  #  Subnet            Network ID     First Host     Last Host      Broadcast      Netmask          Wildcard  Hosts
  ─────────────────────────────────────────────────────────────────────────────────────────────────────────────────
  1  192.168.1.0/26    192.168.1.0    192.168.1.1    192.168.1.62   192.168.1.63   255.255.255.192  0.0.0.63  62
  2  192.168.1.64/26   192.168.1.64   192.168.1.65   192.168.1.126  192.168.1.127  255.255.255.192  0.0.0.63  62
  3  192.168.1.128/26  192.168.1.128  192.168.1.129  192.168.1.190  192.168.1.191  255.255.255.192  0.0.0.63  62
  4  192.168.1.192/26  192.168.1.192  192.168.1.193  192.168.1.254  192.168.1.255  255.255.255.192  0.0.0.63  62

When N is not a power of two, the next power is used and the first N subnets are shown.

JSON for scripts

cidr 10.0.0.0/30 --json

{
  "input": "10.0.0.0/30",
  "address": "10.0.0.0",
  "network": "10.0.0.0/30",
  "version": 4,
  "network_id": "10.0.0.0",
  "broadcast": "10.0.0.3",
  "netmask": "255.255.255.252",
  "wildcard": "0.0.0.3",
  "prefix": 30,
  "first_host": "10.0.0.1",
  "last_host": "10.0.0.2",
  "usable_hosts": 2,
  "total_addresses": 4,
  "type": "Private (RFC 1918)"
}

# Usable hosts of a network, straight into a variable
hosts=$(cidr 10.20.0.0/22 --json | jq .usable_hosts)

Binary and IPv6

cidr 192.168.1.0/24 -binary
cidr 2001:db8::/32 -divide 16

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🧪 Development

pip install -e ".[dev]"
ruff check .
pytest

See CHANGELOG.md for release notes.

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📝 License

MIT — see LICENSE.

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💬 Feedback

Open an issue or reach out via GitHub.

🌐 Connect