Subnet Calculator

Subnet Calculator features

• 01

  CIDR or IP + mask

  Accepts 192.168.1.0/24 or 192.168.1.0 255.255.255.0, and even a bare address (treated as /32). It figures out the prefix and validates the mask is contiguous.

• 02

  Every derived value

  Network, broadcast, first and last usable host, usable host count, netmask, and wildcard mask are laid out at a glance — the numbers you need to plan or troubleshoot a subnet.

• 03

  Correct edge cases + binary

  /31 links show two usable hosts per RFC 3021 and /32 shows a single host, instead of the misleading zeroes many calculators give. A binary breakdown of network, mask, and broadcast helps you see the boundary.

Subnet Calculator FAQ

How many usable hosts are in a /24?

A /24 has 256 total addresses and 254 usable hosts — the first is the network address and the last is the broadcast, both reserved. This calculator shows the usable count for any prefix automatically.

What is the broadcast address of a subnet?

It's the last address in the block, formed by setting all host bits to 1. Traffic sent to it reaches every host on the subnet. Enter your CIDR and the broadcast is shown alongside the network address.

How does a /31 subnet work?

RFC 3021 defines /31 for point-to-point links: both of its two addresses are usable, with no separate network or broadcast address. This tool reflects that, showing two usable hosts rather than zero.

What is a wildcard mask?

A wildcard mask is the bitwise inverse of the netmask (for /24 it's 0.0.0.255). It's used in ACLs and routing configs on Cisco-style devices to indicate which bits can vary. The calculator shows it next to the netmask.

How do I convert CIDR to a subnet mask?

Enter the CIDR prefix (say /26) and the tool displays the equivalent dotted-decimal netmask (255.255.255.192) along with all other subnet details. No lookup table needed.