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IP Subnet Calculator

Calculate network information from an IPv4 address in CIDR notation.

Overview

  • Calculates the network address, broadcast address, usable host count, and more from an IPv4 address in CIDR notation (e.g. 192.168.1.0/24).
  • Even if you enter an address with host bits set (such as 192.168.1.200/24), it is automatically normalized to that subnet's network address before calculating.
  • Also handles special prefix lengths such as /31 (a point-to-point link per RFC 3021) and /32 (a single host).

Usage

  1. Enter an address in "IP address/prefix length" format (e.g. 192.168.1.0/24).
  2. Click "Calculate".
  3. The network address, broadcast address, subnet mask, usable host count, and more are displayed.

Example

Input

192.168.1.10/24

Output

Network: 192.168.1.0 / Broadcast: 192.168.1.255 / Usable hosts: 254

Use Cases

  • Checking the usable host count and address range of a subnet being allocated during network design
  • Understanding the actual network range from a CIDR notation found in a server or router configuration
  • Verifying subnetting calculations before writing them into a design document

FAQ

What happens if I enter an address with host bits set (e.g. 192.168.1.200/24)?

It is automatically normalized to that subnet's network address before calculation.

How are /31 and /32 handled?

/32 is treated as a single host (network, broadcast, and host are all the same address). /31 is treated as a point-to-point link per RFC 3021, where both addresses are usable.

Is IPv6 supported?

Currently only IPv4 is supported.

Notes

  • Currently only IPv4 is supported. IPv6 addresses cannot be handled.
  • /32 is treated as a single host (network, broadcast, and host are all the same address).
  • /31 is treated as a point-to-point link per RFC 3021, where both addresses are usable (its usable host count is counted differently from a normal subnet).

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