Subnet Calculator

IPv4 CIDR subnet calc: network, broadcast, mask, hosts.

A free IPv4 subnet calculator: enter an address with a CIDR prefix (e.g. 192.168.1.10/24) to get the network address, broadcast address, subnet mask, wildcard mask, usable host range and host count. It computes locally with 32-bit integer math.

How to use

1. Enter an IPv4 address with a prefix, e.g. 10.0.0.5/22.
2. Read the network, broadcast, mask, wildcard, host range and count.
3. Change the prefix to recompute live.

FAQ

What does the CIDR prefix (/24) mean?

The prefix is the number of leading 1-bits in the subnet mask. /24 means the first 24 bits are the network part (mask 255.255.255.0), leaving 8 bits for hosts.

Why are there two fewer usable hosts than total addresses?

In each subnet the first address is the network and the last is the broadcast, normally not assigned to hosts, so usable = 2^(32−prefix) − 2. Exceptions: /31 makes both addresses usable (RFC 3021), and /32 is a single address.

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