Subnet calculator

Free IPv4 subnet calculator. Enter CIDR notation and get the network address, broadcast, netmask, first and last host, and usable host count.

Free tool

Subnet Calculator

Enter a network in CIDR notation, like 192.168.1.0/24, and get every derived value instantly: network and broadcast addresses, netmask, the usable host range, and how many hosts fit. Pure math, computed in your browser.

Subnet calculator

What does the /24 in CIDR notation mean?

The number of leading bits that identify the network. A /24 fixes the first 24 bits, leaving 8 for hosts — 256 addresses, 254 usable after the network and broadcast addresses are reserved.

Why are two addresses in every subnet unusable?

The all-zeros host address names the network itself and the all-ones address is the broadcast. The /31 and /32 special cases used for point-to-point links and single hosts are the exception.

This tool also lives in the homepage tool drawer alongside 17 others. Browse everything on the tools page or look up any address with the IP lookup.