Subnet calculator

What it does: does the math of a subnet for you — given a network, it tells you the address range it covers, the first and last usable addresses, the broadcast address, the mask, and how many hosts fit. It's the everyday "what does /24 actually mean here?" calculator.

What you need: an IPv4 network in CIDR form (e.g. 192.168.1.0/24) or an IPv4 address plus a mask. That's it — no connection at all. (IPv6 isn't supported yet.)

Safe to run: yes, and fully offline — it's pure math, touches no network.

What to expect / reading results: enter 192.168.1.0/24 and you get network 192.168.1.0, usable .1–.254, broadcast .255, 254 hosts. Use it to plan address ranges: work out what a block covers before you assign it. For newcomers to CIDR: The /number is how many bits are fixed — bigger number = smaller network.