IP Subnet Calculator
Instantly calculate the network address, mask, usable address range and broadcast address of an IPv4 network.
How it works
An IPv4 address in CIDR notation, such as 192.168.1.0/24, combines an address with a prefix indicating how many bits are reserved for the "network" part (here 24 out of 32). From this prefix, you can derive the subnet mask, the network address (first address of the block), the broadcast address (last address of the block, reserved for broadcasting) and the range of addresses actually usable for machines on this network. This is exactly what an administrator or developer needs to do before configuring a router, a home gateway, or an addressing plan for a local network.
Why is the number of usable addresses lower than the total?
In a classic network, the first address of the block (the network address) and the last one (the broadcast address) are reserved and cannot be assigned to a device: they serve respectively to identify the network itself and to broadcast a message to all devices on the network. That's why the number of usable addresses equals the total minus 2, except for /31 and /32 prefixes, which follow special rules (point-to-point links or single host).
What network size should I choose for a home local network?
A /24 prefix (mask 255.255.255.0) offers 254 usable addresses, more than enough for most home or small-office networks. A larger prefix (like /28, 14 usable addresses) suits a smaller subnet, while a smaller prefix (like /16) is reserved for much larger corporate networks.
Privacy: the calculation runs entirely in your browser via WebAssembly — the address entered is never sent to a server.