Subnet Calculator

The number of available network and host addresses are derived from the number of bits used for subnet masking. CIDR notation is a compact representation of an IP address and its associated routing prefix.

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Any private key value that you enter or we generate is not stored on this site, this tool is provided via an HTTPS URL to ensure that private keys cannot be stolen, for extra security run this software on your network, no cloud dependency

A broadcast address is a logical address at which all devices connected to a multiple-access communications network are enabled to receive datagrams.
A message sent to a broadcast address is typically received by all network-attached hosts, rather than by a specific host

For example A /24 network may be divided into the following subnets by increasing the subnet mask successively by one bit. This affects the total number of hosts that can be addressed in the /24 network

Prefix size Subnet mask Available
Usable hosts
per subnet
usable hosts
/24 1 254 254
/25 2 126 252
/26 4 62 248
/27 8 30 240
/28 16 14 224
/29 32 6 192
/30 64 2 128
/31 128 *


The following special addresses and networks exist in IPv4: the "ANY" address that is used by programs to speak to all network interfaces, it is never used directly. The whole network 0.*.*.* is reserved for special purposes (like DHCP).
172.16.*.* - 172.31.*.*
RFC Definend private address is the localhost address The entire 127.*.*.* network is reserved for (host-)local networking.
169.254.*.* Link-Local addresses. These are automatically generated by some operating systems and (e.g. MacOS and Linux with Avahi installed) and are only usable for local communication in the LAN segment.
198.18.*.* - 198.19.*.* Network benchmark tests, this should never be used in production networks.
TEST-NET-2, Documentation and examples
TEST-NET-3, Documentation and examples
224.*.*.* Multicasts (former Class D network) - e.g. there is no default gateway or broadcast for multicasting Reserved (former Class E network) Link Broadcast - this is sent to all hosts on the same network link, but does not cross routers