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NETWORK TOOLS

IP/CIDR Subnet Calculator

Enter an IPv4 CIDR block to calculate subnet mask, network address, broadcast address, first and last host, and address counts.

Tool statusRuns in your browser
Preview

IPv4 CIDR

Initial support for IPv4.

Subnet

Mask
255.255.255.0
Network
192.168.1.0
Broadcast
192.168.1.255
First host
192.168.1.1
Last host
192.168.1.254
Addresses
256
Usable hosts
254

How it works

  1. Enter your input

    Fill in the values, paste your text, or upload the file this tool works with.

  2. See results instantly

    Most tools update live as you type; a few use a single button. Either way, the result appears right on this page.

  3. Use your results

    Copy, download, or share what the tool produces — you're always in control of the output.

Privacy and processing — Runs locally in your browser. This tool does not upload your input.

What is IP/CIDR Subnet Calculator?

Enter an IPv4 CIDR block to see the subnet mask, network address, broadcast address, host range, and address counts.

UNDERSTAND THE TOOL

How to calculate IPv4 subnets

CIDR input

Use the format address/prefix, such as 192.168.1.10/24. Each octet must be between 0 and 255, and the prefix length must be between 0 and 32.

Host ranges

For most subnets, the first usable host is one address after the network and the last usable host is one before broadcast. /31 is treated as a two-address point-to-point link, and /32 as a single host route.

What to use it for

  • Check network and broadcast addresses before configuring a device.
  • Estimate usable host capacity for an IPv4 subnet.
  • Verify whether a CIDR block is too broad or too narrow for a planned range.

CIDR example

Mask
cidr = 24 -> 255.255.255.0
Usable hosts
/24 -> 2^(32 - 24) - 2

192.168.1.10/24

Network is 192.168.1.0, broadcast is 192.168.1.255, and usable hosts run from .1 to .254.

2^8 - 2 = 254 usable hosts

Subnet notes

The calculator covers IPv4 CIDR only. IPv6 planning needs a different subnet model and is not part of this tool.

Frequently Asked Questions

Does it support IPv6?

No. This version is focused on IPv4 CIDR blocks.

Why does /31 show two usable hosts?

A /31 is commonly used for point-to-point links under RFC 3021, where both addresses can be used.

What does /32 mean?

It represents exactly one IPv4 address, often used as a host route.

Can I enter a range without CIDR?

No. Enter one IPv4 address with a CIDR prefix, such as 10.0.0.15/28.

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