toolkit

CIDR Calculator

Runs in browser

Calculate network ranges and subnets

Quick Reference

/32 (1 host)
/24 (256 hosts)
/16 (65k hosts)
/8 (16M hosts)

How to Use

Enter a CIDR block (e.g. 10.0.0.0/16).

You will see:

  • Network Range (First/Last IP)
  • Number of Usable Hosts
  • Netmask & Broadcast IP
  • Binary Visualization

Network Range

Private (Class C)
First Host
192.168.1.1
Last Host
192.168.1.254
Total Hosts
254
Netmask
255.255.255.0

Technical Details

CIDR IP 192.168.1.0
Broadcast 192.168.1.255
Binary Netmask 0-111111.01010111.11111111.00000000
/24 Mask Bits

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About CIDR Calculator

What is CIDR?

CIDR (Classless Inter-Domain Routing) is a method for allocating IP addresses and for IP routing. It was introduced in 1993 to replace the previous classful network architecture design.

Understanding Subnet Masks

The Syntax

CIDR notation consists of an IP address, a slash, and a number (e.g., 192.168.1.0/24). The number denotes how many bits are used for the network prefix.

Usable Hosts

The formula to calculate usable hosts is 2^(32 - mask) - 2. We subtract 2 for the Network Address (start) and Broadcast Address (end).

Common Networks Cheat Sheet

CIDR Netmask Hosts Use Case
/32 255.255.255.255 1 Single IP
/30 255.255.255.252 2 Point-to-Point Links
/24 255.255.255.0 254 Standard LAN / Office
/16 255.255.0.0 65,534 Large Campus / VNet

💡 Pro Tip: Private Ranges

  • 10.0.0.0/8 (Large networks)
  • 172.16.0.0/12 (AWS/Cloud often use this)
  • 192.168.0.0/16 (Home routers)

Further Reading