Help

SubnetCalc calculates the network data for IPv4 and IPv6 addresses: network, broadcast, host range, subnet mask and much more. All calculations run entirely in your browser – no data is sent to any server.

Entering an address

The Address section is where you start. Switch between IPv4 and IPv6, then type an address, for example 192.168.1.5 or 2001:db8::1. The version is detected automatically when you include a :. You can also enter the prefix directly in the address, e.g. 192.168.1.5/24.

Prefix and subnet mask

• The prefix length slider sets the number of network bits (0–32 for IPv4, 0–128 for IPv6). Use the − and + buttons for fine adjustment.
• For IPv4 you can enter the subnet mask directly (e.g. 255.255.255.0) – the prefix is derived automatically. In IPv6 the mask is implicit from the prefix.

Presets

The Presets section contains ready-made example addresses for IPv4 and IPv6. Click one to load it – ideal for trying out the calculator.

Results

The results show the network address, broadcast (IPv4) or last address (IPv6), the first and last usable host, the usable host count and, for IPv4, the CIDR class and wildcard mask. For IPv4 a binary view and the CIDR quick reference table are also displayed.

Subnet plan

Activate the Show subnet list toggle and choose a subnet size with the Divide into / slider. SubnetCalc lists every subnet of the network with its host range, broadcast and number of hosts.

Bits

The Bits section shows the breakdown into network bits and host bits for the current prefix.