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CIDR Calculator

Calculate network, broadcast, usable hosts, subnet mask, and wildcard for any IPv4 CIDR

Input
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Output

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What is CIDR Calculator

Last reviewed:

CIDR Calculator takes any IPv4 CIDR block (e.g. `192.168.1.0/24`) and returns the network address, broadcast, usable host range, subnet mask, wildcard, and total IP count.

It's handy for planning subnets, provisioning cloud VPCs, and validating firewall rules without relying on command-line tools.

Why use it

  • Plan AWS / Azure VPC subnets.
  • Calculate usable host counts for firewalls.
  • Verify ACL rules and CIDR ranges.
  • Teach subnetting with worked examples.
  • Convert between CIDR prefixes and masks.

Features

  • Network + broadcast + mask + wildcard
  • Usable host range & count
  • Handles /31 and /32 edge cases
  • IPv4 /0 through /32
  • CIDR never leaves your machine

How to use CIDR Calculator

  1. Paste CIDR. Use the form `x.x.x.x/prefix`.
  2. Run. Review the full report.
  3. Use values. Copy mask, hosts, or range into your tooling.

Example (before/after)

Input

192.168.1.0/26

Report

Input:       192.168.1.0/26
Prefix:      /26
Subnet mask: 255.255.255.192
Wildcard:    0.0.0.63
Network:     192.168.1.0
Broadcast:   192.168.1.63
First host:  192.168.1.1
Last host:   192.168.1.62
Usable hosts: 62
Total IPs:   64

Common errors

Off-by-one hosts

Host count is network size − 2 (for network + broadcast).

Fix: The tool handles /31 and /32 edge cases correctly.

IPv6

This tool handles IPv4 only.

Fix: For IPv6, use a dedicated IPv6 subnet tool.

FAQ

Does it handle /31 and /32?

Yes — /31 reports 0 usable hosts (point-to-point) and /32 reports 0 hosts (host route).

Is input uploaded?

No — calculations run client-side.

What prefixes are supported?

/0 through /32.

Does it show the wildcard mask?

Yes — useful for Cisco ACL rules.

IPv6 support?

Not yet — this tool is IPv4-only.

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